Tubular flame burner

ABSTRACT

A tubular flame burner including a tubular combustion chamber having two ends, wherein one end is an open front-end and the other end is a rear-end to which an ignition device is mounted; and fuel-gas spraying nozzles and oxygen-containing-gas spraying nozzles, wherein respective orifices of the respective nozzles face toward an inner surface of the combustion chamber, so as to spray a fuel-gas and an oxygen-containing-gas in a neighborhood of a tangential direction of an inner circumferential wall of the combustion chamber; wherein an ignition device is disposed at a position between a point of a tube axis extending along a longitudinal direction of the combustion chamber, and a point of an axis apart away, by ½ of a radius of the combustion chamber, from the point of the tube axis along a cross-sectional direction orthogonal to the longitudinal direction.

This application is a Divisional application of application Ser. No.10/514,668 filed Jan. 4, 2005, which is the United States national phaseapplication of International application PCT/JP2003/010059 filed Aug. 7,2003. The entire contents of each of application Ser. No. 10/514,668 andInternational application PCT/JP2003/010059 are incorporated byreference herein.

TECHNICAL FIELD

The present invention relates to a burner included in a furnace or acombustion chamber. The present invention relates to a combustion burnerincluded and used in an industrial furnace or a combustion chamber.

BACKGROUND OF THE INVENTION

In general, an industrial-use gas burner has been known such as aconfiguration whose flame is formed in front of the tip of a burner.Concerning such a burner, fuel supplied through a fuel-passage andcombustion air supplied through an air-passage are sprayed in front ofthe burner from the nozzle, resulting in forming the turbulence by thesprayed air and fuel.

Accordingly, the combustion flame becomes turbulent, and the partialflame extinction happens. Such partial flame extinction makes thecombustion not stable. In order to avoid such a phenomenon as much aspossible, nozzle is designed to exhibit the optimal nozzle-flow-velocityso that stable combustion is obtained, which corresponds to theparticular heating value and combustion speed of the employed fuel fromthe thermal perspective and the perspective of fluid dynamics:

In such a case, the stable combustion is done when using the fuelsuitable for the designed nozzle. On the other hand, combustion becomesunstable when using other kinds of fuel.

Furthermore, combustion reaction is always performed within a flame thathas a certain volume, so the reaction is required to continue for a longperiod. In such a case, NOx or soot is apt to generate by the reason ofthe long combustion time. And, the flame has a partial high-temperatureregion and a low-temperature region, wherein NOx is easy to generate inthe high-temperature region, and soot is easy to generate in thelow-temperature region.

On the other hand, a tubular flame burner is disclosed in JapaneseUnexamined Patent Application Publication No. 11-281015. Thispublication includes a tubular combustion chamber of which one-end opensand a nozzle for spraying a fuel gas and a nozzle for spraying anoxygen-containing-gas in the neighborhood of the closed end thereof.Here, the nozzle is located, facing in the tangential direction of theinner circumferential wall of the aforementioned combustion chamber.

With the aforementioned tubular flame burner, stable flame is formed ina high-speed swirl within the burner, accordingly combustion isperformed with small irregularities in the temperature of a combustionflame. Therefore, no partial high-temperature regions are easy to beformed. Furthermore, stable combustion is achieved even with a lowoxygen ratio or air excess ratio. Consequently, the tubular flame burnerhas the advantage to reduce harmful substances such as NOx or the like,unburned portions of hydrocarbon or the like, and environmentalpollutants such as soot and the like, as well as to reduce of the sizethereof.

FIG. 8 is explanatory diagrams which show an conventional tubular flameburner, wherein FIG. 8A is a configuration diagram which shows thetubular flame burner, and FIG. 8B is a cross-sectional view taken alongline B-B in FIG. 8A. The tubular flame burner includes a tubularcombustion chamber 121, whose one end opens for serving as an exhaustvent for an exhaust gas. Furthermore, the tubular flame burner includeslong slits on the other end along the tube axis, each of which areconnected to one of nozzles 122 for separately supplying a fuel gas anda nozzle for supplying an oxygen-containing-gas.

The nozzles 122 are disposed in a tangential direction of the inner wallof the combustion chamber 121 for spraying the fuel gas and theoxygen-containing-gas so as to form a swirl thereof within thecombustion chamber 121. Furthermore, the tip of each nozzle 122 isformed flat with a reduced orifice for spraying the fuel gas and theoxygen-containing-gas at high speed. Note that reference numeral 123denotes a spark plug.

In the above-mentioned burner having such a configuration, when amixture gas is ignited, which forms a swirl (such a swirl is generatedby the fuel gas and the oxygen-containing-gas sprayed from the nozzles122), the gas within the combustion chamber 121 is stratified intoconcentric gas layers with different densities, due to difference in thedensity of the gas and the centrifugal force. That is to say, ahigh-temperature and low-density exhaust gas exists close to the axis ofthe combustion chamber 121, and a high-density unburned gas exists closeto the inner wall of the combustion chamber 121 (away from the axisthereof). This state exhibits remarkable stability from the viewpoint offluid dynamics. In this case, a tube-shaped flame is formed, and the gasflow is stratified into stable layers, thereby forming a film-shapedstable flame. The position of the flame is determined, being influencedby the position, wherein two factors (one is the exhaust gas speedtoward the center of the combustion chamber 121 and the other is theflame propagation speed) balance each other in natural process. In FIG.8A, reference numeral 124 denotes a tube-shaped flame.

Furthermore, an unburned low-temperature gas forms a boundary layer nearthe inner wall of the combustion chamber. Accordingly, the wall of thecombustion chamber 121 is not heated by the direct heat transfer to adegree of a high temperature, resulting in avoiding the thermal loss,which means, preventing the heat from releasing to the outside of thewall. That is to say, the aforementioned burner has the effectiveadvantage on great thermal insulation, thereby maintaining thermalstability of combustion.

The gas within the combustion chamber 121 flows downstream whileswirling, and at the same time, the mixture gas around the inner wallcontinuously burns so as to form a tubular flame. And, a generatedexhaust gas flows toward the axis of the combustion chamber 121 so as tobe discharged from the open-end.

However, the conventional tubular flame burner having such aconfiguration happens to have problems as follows. That is to say:

In general, a fuel gas that has a small heating value invites adisadvantage, that is, the range of the air excess ratio is extremelynarrow, taking into consideration the usable range for igniting byelectronic spark. Therefore, it is extremely difficult to ignite such afuel without premixing of the fuel gas and the oxygen-containing-gas.

The aforementioned tubular flame burner has the same difficult problemon igniting by the electronic spark due to the limited range of the airexcess ratio of the fuel gas and the oxygen-containing-gas suitable forthe ignition. Accordingly, it may be a case, the aforementioned tubularflame burner requires a pilot burner.

Furthermore, the conventional tubular flame burner has such problems asthe following description.

(1) In particular, in case of using oil fuel or heavy-hydrocarbon fuelsuch as a propane gas, the free carbon content within the fuel emitslight during combustion, resulting in forming a luminous flame. Theluminous flame has such a characteristic that the radiation rate is highby himself, resulting in increasing radiation heat from the luminousflame. Accordingly, when the burner having a configuration, whoseluminous flame is located in the position capable of viewing from theheated material, the aforementioned burner exhibits high heat transferefficiency. However, with the aforementioned conventional burner, thefuel sprayed into the furnace does not form a luminous flame, but formsa transparent exhaust gas that has small emissivity due to the completecombustion of the fuel within the combustion chamber. This leads tosmall heat transfer efficiency of the combustion method with theconventional tubular burner.(2) With the conventional tubular burner, no soot is generated due tocomplete combustion of the fuel. Accordingly, the conventional tubularburner is not used in case of requiring soot, for example, such ascarburizing steel with high efficiency, for example.(3) The conventional tubular burner exhibits excellent combustionperformance due to complete combustion of the fuel within the combustionchamber, but NOx is easy to be generated.

Furthermore, the conventional tubular flame burner has a configuration,wherein, in order to form a tubular flame, the respective supply nozzlesthat are flat along the tube axis are connected to the slits extendingalong the tube axis. (The slits are located in the tubular combustionchamber.) The conventional tubular flame burner is used while sprayingthe fuel gas and the oxygen-containing-gas into the combustion chamber,simultaneously with forming high-speed swirl of the sprayed fuel gas andthe oxygen-containing-gas. Accordingly, the conventional tubular flameburner causes such a problem that relatively high pressure loss happensat the slits. That is to say, in general, the fuel gas and theoxygen-containing-gas are supplied with a constant pressure.Accordingly, there is need to increase the flow of the fuel gas and theoxygen-containing-gas, in case of increasing the combustion load. But inthis case, the pressure loss at the slits increases, proportional to thesquire value of the flow speed, ending up in a small increase in acombustion load.

Contrarily, when the conventional tubular flame burner having aconfiguration is used (wherein each slit is formed with an increasedcross-sectional area so as to reduce the pressure loss at the slit), theflow speed of the fuel gas and the oxygen-containing-gas remarkablyreduce along the tangential direction of the inner wall of thecombustion chamber. Such reduction happens in the event that combustionis performed with a small flow of the fuel gas and theoxygen-containing-gas corresponding to a small combustion load.Accordingly, a tube-shaped flame is not formed, leading to such aproblem as increased amount of NOx, soot, and the like, generated in thecombustion chamber.

As described above, concerning the conventional tubular flame burner,the problem is as follows. In the event that the supply flow of the fuelgas and the oxygen-containing-gas is adjusted corresponding to thechange in the combustion load, it may be a case, the flow speed of thefuel gas and the oxygen-containing-gas is out of the range of thesuitable flow speed. The suitable flow speed is determined between theflame formation minimal flow speed required for formation of atube-shaped flame and the permissive maximal flow speed dependent uponthe pressure loss, inviting difficulty in stable combustion in a widerange of the combustion load, and resulting in a narrow range of thecombustion load suitable for the conventional tubular flame burner.

Furthermore, there is need to further improve the aforementionedconventional tubular flame burner in order to employ fuel with lowerheat output so as to improve the practical use.

Accordingly, the present invention has been conceived in order to solvethe aforementioned problems of the conventional tubular flame burner.And the present invention has been conceived and studied in order toprovide a tubular flame burner having a new flame formation mechanism,wherein various kinds of fuel can be used, wherein combustion isperformed in a wide combustion range, and wherein stable combustion ismaintained even with a wide range of the change in combustion load. Andin the present invention, stable combustion can be performed, anddischarge of an environmental pollution substance created due tocombustion is prevented.

SUMMARY OF THE INVENTION

The present invention comprises the following devices and methods inorder to solve the above-described conventional problems. That is tosay:

Firstly, a tubular flame burner comprises:

a tubular combustion chamber having two ends of an open end and a closedend including an ignition device; and

fuel-gas spraying nozzles and oxygen-containing-gas spraying nozzles,each orifice of which faces toward the inner face of the combustionchamber so as to spray a fuel gas and an oxygen-containing-gas in aneighborhood of a tangential direction of the inner circumferential wallof the combustion chamber;

wherein the ignition device is disposed at a position between

-   -   a point of the tube axis extending along the longitudinal        direction of the combustion chamber, and    -   a point of an axis away from the tube axis along the        cross-sectional direction orthogonal to the longitudinal        direction thereof by ½ of the radius thereof.

Secondly, a tubular flame burner comprises:

a tubular combustion chamber wherein the front-end opens; and

fuel-gas spraying nozzles and oxygen-containing-gas spraying nozzles,each orifice of which faces toward the inner face of the combustionchamber so as to spray a gas in a neighborhood of a tangential directionof the inner circumferential wall of the combustion chamber,

wherein a tube as a component of the combustion chamber, wherein thefuel and the oxygen-containing-gas are discharged from the nozzleorifices of the combustion chamber, is formed of an inner tube and anouter tube for adjusting the length of the combustion chamber by slidingthe outer inner face along the outer face of the inner tube.

Thirdly, a tubular flame burner comprises:

a tubular combustion chamber wherein the front-end opens; and

fuel-gas spraying nozzles and oxygen-containing-gas spraying nozzles,each orifice of which faces toward the inner face of the combustionchamber, which can spray gas in a neighborhood of a tangential directionof the inner circumferential wall of the combustion chamber, forseparately spraying fuel and an oxygen-containing-gas, or spraying apremixed gas,

wherein the tubular flame burner is formed of a plurality of the tubularflame burners,

and wherein the tubular flame burner is a multi-stage tubular flameburner having a configuration, wherein the rear-end of the tubular flameburner with a greater inner diameter of the combustion chamber isconnected to the front-end of the tubular flame burner with a smallerinner diameter of the combustion chamber. In such a way, the multi-stagetubular flame burner is formed.

Fourthly, a tubular flame burner comprises:

a tubular combustion chamber wherein the front-end opens;

fuel-gas spraying nozzles and oxygen-containing-gas spraying nozzles,each orifice of which faces toward the inner face of the combustionchamber, which can spray gas in a neighborhood of a tangential directionof the inner circumferential wall of the combustion chamber; and

an outer tube with a longer inner diameter than the outer diameter ofthe combustion chamber, which covers the combustion chamber;

wherein a gap between the outer face of the combustion chamber and theinner face of the outer tube provides a passage for a fuel gas or anoxygen-containing-gas to pass before supplying these gases to thespraying nozzles.

Fifthly, a combustion controller for a tubular flame burner comprises:

a tubular combustion chamber wherein the front-end opens;

a plurality of fuel-gas spraying nozzles and a plurality ofoxygen-containing-gas spraying nozzles, each orifice of which facestoward the inner face of the combustion chamber, for spraying generallytoward a tangential direction of the inner circumferential wall of thecombustion chamber. Here, these nozzles are disposed along at least onedirection of the longitudinal direction and the circumferentialdirection;

switching valves disposed on supply lines, wherein each of the switchingvalves are connected to the corresponding one of the nozzles included inthe tubular flame burner; and

means for controlling on/off of the switching valves so that thespraying speed from the nozzles is maintained in a predetermined rangecorresponding to the combustion load applied to the tubular flameburner.

Sixthly, a combustion controller for a tubular flame burner comprises:

a tubular flame burner comprising:

-   -   a tubular combustion chamber, wherein the front-end opens; and    -   a plurality of nozzles, each orifice of which faces toward the        inner face of the combustion chamber, for spraying a premixed        gas formed of a fuel gas and an oxygen-containing as in a        neighborhood of a tangential direction of the inner        circumferential wall of the combustion chamber. Here, these        nozzles are disposed along at least one direction of the        longitudinal direction and the circumferential direction;

switching valves disposed on supply lines each of which are connected tothe corresponding one of the nozzles; and

control means for controlling on/off of the switching valves so that thespraying speed from the nozzles is maintained in a predetermined rangecorresponding to the combustion load applied to the tubular flameburner.

Seventhly, a combustion controller for a tubular flame burner comprises:

a tubular flame burner comprising:

-   -   a tubular combustion chamber, wherein the front-end opens; and    -   a plurality of fuel-gas spraying nozzles and a plurality of        oxygen-containing-gas spraying nozzles, each orifice of which        faces toward the inner face of the combustion chamber, for        spraying in a neighborhood of a tangential direction of the        inner circumferential wall of the combustion chamber;    -   switching valves disposed on supply lines, wherein the        respective switching valves are connected to the corresponding        one of the nozzles included in the tubular flame burner;    -   control means for controlling on/off of the switching valves so        that the spraying speed from the nozzles is maintained in a        predetermined range corresponding to the combustion load applied        to the tubular flame burner;    -   adjusting means for adjusting the aperture area of each nozzle        orifice to be variable; and    -   control means for adjusting the aperture area of each nozzle        orifice to be variable by controlling the adjusting means so        that the spraying speed from the nozzles is maintained in a        predetermined range corresponding to the combustion load applied        to the tubular flame burner.

Eighthly, a combustion controller for a tubular flame burner comprises:

a tubular flame burner comprising:

-   -   a tubular combustion chamber wherein the front-end opens; and    -   a plurality of fuel-gas spraying nozzles and a plurality of        oxygen-containing-gas spraying nozzles, wherein each orifice of        the nozzle faces toward the inner face of the combustion        chamber, for spraying a premixed gas formed of a fuel gas and an        oxygen-containing-gas in a neighborhood of a tangential        direction of the inner circumferential wall of the combustion        chamber;

switching valves disposed on supply lines, wherein each of the switchingvalves are connected to the corresponding one of the nozzles included inthe tubular flame burner;

control means for controlling on/off of the switching valves so that thespraying speed from the nozzles is maintained in a predetermined rangecorresponding to the combustion load applied to the tubular flameburner;

adjusting means for adjusting the aperture area of each nozzle orificeto be variable; and

control means for adjusting the aperture area of each nozzle orifice tobe variable by controlling the adjusting means so that the sprayingspeed from the nozzles is maintained in a predetermined rangecorresponding to the combustion load applied to the tubular flameburner.

Ninthly, a combustion control method for a tubular flame burnercomprises:

a step for preparing a tubular combustion chamber, wherein the front-endopens, and a plurality of fuel-spraying nozzles and a plurality ofoxygen-containing-gas spraying nozzles. Here, each nozzle orifice facesthe inner wall of the combustion chamber, disposed along at least onedirection of the longitudinal direction and the circumferentialdirection;

a step for connecting supply lines to the nozzles, and providingswitching valves to the supply lines;

a step for adjusting the fuel-spraying nozzles and theoxygen-containing-gas spraying nozzles so that each spraying directionis in a neighborhood of a tangential direction of the innercircumferential wall of the combustion chamber, to control combustion;and

a step for controlling on/off of the switching valves so that thespraying speed from the nozzles is maintained in a predetermined rangecorresponding to the combustion load applied to the tubular flameburner.

Tenthly, a method for controlling a combustion by a tubular flame burnercomprising:

a step for preparing a tubular combustion chamber wherein the front-endopens, and for preparing a plurality of nozzles, wherein each nozzleorifice faces the inner wall of the combustion chamber, for spraying apremixed gas formed of a fuel gas and an oxygen-containing-gas andwherein each nozzle orifice is disposed along at least one direction ofthe longitudinal direction and the circumferential direction;

a step for connecting supply lines to the nozzles, and providingswitching valves to the supply lines;

a step for adjusting the fuel-spraying nozzles to be variable and theoxygen-containing-gas spraying nozzles so that each spraying directionis in a neighborhood of a tangential direction of the innercircumferential wall of the combustion chamber, to control combustion;and

a step for controlling on/off of the switching valves so that thespraying speed from the nozzles is maintained in a predetermined rangecorresponding to the combustion load applied to the tubular flameburner.

Eleventh, a method for controlling combustion by a tubular flame burnercomprises:

a step for preparing a tubular combustion chamber wherein the front-endopens, and a plurality of fuel-spraying nozzles and a plurality ofoxygen-containing-gas spraying nozzles, wherein each nozzle orificefaces the inner wall of the combustion chamber;

a step for connecting supply lines to the nozzles, and for providingswitching valves to the supply lines;

a step for adjusting the fuel-spraying nozzles and theoxygen-containing-gas spraying nozzles so that each spraying directionis in a neighborhood of a tangential direction of the innercircumferential wall of the combustion chamber, to control combustion;

a step for controlling on/off of the switching valves so that thespraying speed from the nozzles is maintained in a predetermined rangecorresponding to the combustion load applied to the tubular flameburner; and

a step for adjusting the apertures area of the nozzle orifices so thatthe spraying speed from the nozzles is maintained in a predeterminedrange corresponding to the combustion load applied to the tubular flameburner by adjusting means for adjusting the apertures area of the nozzleorifices.

Twelfth, a method for controlling combustion by a tubular flame burnercomprises:

-   -   a step for preparing: a tubular combustion chamber whose        front-end opens, and a plurality of nozzles whose each nozzle        orifice faces the inner wall of the combustion chamber, for        spraying a premixed gas formed of a fuel gas and an        oxygen-containing-gas;    -   a step for connecting supply lines to the nozzles, and providing        switching valves to the supply lines;    -   a step for adjusting the nozzles so that each spraying direction        is in a neighborhood of a tangential direction of the inner        circumferential wall of the combustion chamber, to control        combustion;    -   a step for controlling on/off of the switching valves so that        the spraying speed from the nozzles is maintained in a        predetermined range corresponding to the combustion load applied        to the tubular flame burner; and,    -   a step for adjusting the apertures area of the nozzle orifices        so that the spraying speed from the nozzles is maintained in a        predetermined range corresponding to the combustion load applied        to the tubular flame burner by adjusting means for adjusting the        apertures of the nozzle orifices.

Thirteenth, a method for controlling combustion by a tubular flameburner comprises:

a step for preparing a tubular combustion chamber whose front-end opens,and whose respective nozzle orifice faces the inner wall of thecombustion chamber for separately spraying fuel and anoxygen-containing-gas, or spraying a premixed gas thereof;

a step for preparing a multi-stage tubular flame burner including aplurality of tubular flame burners that have the respective nozzles,wherein each spraying direction is in a neighborhood of a tangentialdirection of the inner circumferential wall of the combustion chamber,and having a configuration wherein the rear-end of the tubular flameburner with a longer inner diameter of the combustion chamber isconnected to the front-end of the tubular flame burner with a shorterinner diameter of the combustion chamber, whereby the single multi-stagetubular flame burner is formed of the plurality of tubular flameburners; and

a step for controlling combustion by selecting a tubular flame burner tobe used within the plurality of tubular flame burners forming themulti-stage tubular flame burner corresponding to the combustion load.

Fourteenth, a method for controlling combustion by a tubular flameburner comprises:

a step for preparing a tubular combustion chamber formed of an innertube, and an outer tube disposed along the outer circumferential wall ofthe inner tube, wherein the front-end opens, and for preparing fuelspraying nozzles and oxygen-containing-gas, wherein each nozzle orificeare formed on the inner face of the combustion chamber;

a step for adjusting the nozzles so that each spraying direction is in aneighborhood of a tangential direction of the inner circumferential wallof the combustion chamber;

a step for adjusting the length of the combustion chamber by sliding theouter tube;

wherein the outer tube has a combustion chamber whose length is longenough to generate the flame in the combustion chamber in order for thefurnace temperature to reach a predetermined temperature, and further,the outer tube has a combustion chamber whose length is short enough togenerate the flame outside the combustion chamber when the in-furnacetemperature exceeds the predetermined temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a tubular flame burner according to anembodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line A-A in

FIG. 1.

FIG. 3 is an explanatory diagram for describing ignition with a tubularflame burner according to an embodiment of the present invention.

FIG. 4 is a longitudinal cross-sectional view, which shows a tubularflame burner according to an embodiment of the present invention.

FIG. 5 is a diagram which shows the whole length L₁ of the tube-shapedflame formed within the combustion chamber and the length L₂ of thetube-shaped flame formed on the inside and the outside of the combustionchamber.

FIG. 6 is a chart, which shows the relation between L₂/L₄, the heattransfer amount, and the amount of created soot.

FIG. 7 is a chart, which shows the relation between L₂/L₁ and the amountof created NO_(R).

FIG. 8A is an explanatory diagram for describing a conventional tubularflame burner, and is also a configuration diagram of the tubular flameburner.

FIG. 8B is a cross-sectional view taken along line B-B in FIG. 8A.

FIG. 9 is a chart, which shows the furnace temperature and thetemperature of heated steel over time, obtained from a combustion testaccording to the present invention.

FIG. 10 is a chart, which shows the concentration of NO and soot overtime, obtained from a combustion test according to the presentinvention.

FIG. 11 is a chart, which shows the concentration of NO over timeaccording to the present invention.

FIG. 12 is a chart, which shows the concentration of soot over timeaccording to the present invention.

FIG. 13 is a side view of a multi-stage tubular flame burner accordingto an embodiment of the present invention.

FIG. 14A is a cross-sectional view taken along line A-A in FIG. 13.

FIG. 14B is a cross-sectional view taken along line B-B in FIG. 13.

FIG. 15 is an explanatory diagram for describing a combustion controlmethod for a multi-stage tubular flame burner according to an embodimentof the present invention.

FIG. 16 is an explanatory diagram for describing a combustion controlmethod for a multi-stage tubular flame burner according to an embodimentof the present invention.

FIG. 17 is an explanatory diagram for describing a combustion controlmethod for a multi-stage tubular flame burner according to an embodimentof the present invention.

FIG. 18A is an explanatory diagram for describing a tubular flame burneraccording to an embodiment of the present invention, and is also aconfiguration diagram of the tubular flame burner.

FIG. 18B is an explanatory diagram for describing a tubular flame burneraccording to an embodiment of the present invention, and is also across-sectional view taken along line B-B in FIG. 18A.

FIG. 19 is a side view of a tubular flame burner according to anembodiment of the present invention.

FIG. 20A is a cross-sectional view taken along line A-A in FIG. 19.

FIG. 20B is a cross-sectional view taken along line B-B in FIG. 19.

FIG. 21 is an overall configuration diagram, which shows a combustioncontroller for a tubular flame burner according to an embodiment of thepresent invention.

FIG. 22A is an explanatory diagram for describing a combustion controlmethod according to an embodiment of the present invention.

FIG. 22B is an explanatory diagram for describing a combustion controlmethod according to an embodiment of the present invention.

FIG. 23 is a side view of a tubular flame burner according to anembodiment of the present invention.

FIG. 24A is a cross-sectional view taken along line A-A in FIG. 23.

FIG. 24B is a cross-sectional view taken along line B-B in FIG. 23.

FIG. 25 is an overall configuration diagram, which shows a combustioncontroller for a tubular flame burner according to an embodiment of thepresent invention.

FIG. 26 is an overall configuration diagram, which shows a combustioncontroller for a tubular flame burner according to an embodiment of thepresent invention.

FIG. 27 is an overall configuration diagram, which shows a combustioncontroller for a tubular flame burner according to an embodiment of thepresent invention.

FIG. 28 is a side view of a tubular flame burner according to anembodiment of the present invention.

FIG. 29A is a cross-sectional view taken along line A-A in FIG. 28.

FIG. 29B is a cross-sectional view taken along line B-B in FIG. 28.

FIG. 30 is an overall configuration diagram, which shows a combustioncontroller for a tubular flame burner according to an embodiment of thepresent invention.

FIG. 31A is an explanatory diagram for describing a combustion controlmethod according to an embodiment of the present invention.

FIG. 31B is an explanatory diagram for describing a combustion controlmethod according to an embodiment of the present invention.

PREFERABLE EMBODIMENT OF THE INVENTION First Embodiment

FIG. 1 through FIG. 3 show a first embodiment of the present invention.FIG. 1 is a side view of a tubular flame burner according to the presentembodiment, and FIG. 2 is a cross-sectional view taken along line A-A inFIG. 1. FIG. 3 is an explanatory diagram for describing ignition of thetubular burner according to the present embodiment.

In FIG. 1, reference numeral 10 denotes a tubular combustion chamber,wherein the front-end 10 a opens so as to serve as an exhaust vent foran exhaust gas. Furthermore, the tubular combustion chamber 10 includesnozzles near the rear-end 10 b thereof for spraying fuel gas andoxygen-containing-gas into the tubular combustion chamber 10.Furthermore, the tubular combustion chamber 10 includes an ignitionspark plug 21 on the rear-end 10 b thereof for generating a spark withinthe combustion chamber 10 using an igniter 22 and a power supply 23.

As shown in FIG. 1 and FIG. 2, four long and narrow slits 12 are formedalong the tube axis on the circumferential of the tubular combustionchamber 10, serving as nozzles for the combustion chamber 10, whereinthe slits 12 are connected to nozzles 11 a, 11 b, 11 c; and 11 d, formedflat and long and narrow along the tube axis, respectively. Thesenozzles 11 a, 11 b, 11 c, and 11 d, are disposed so that each spraydirection is in a tangential direction of the inner circumferential wallof the combustion chamber 10 so as to form a swirl in a predetermineddirection. Of these four nozzles, the nozzles 11 a and 11 c serve asfuel-gas spraying nozzles, and the nozzles 11 b and 11 d serve asoxygen-containing-gas spraying nozzles.

That is to say, the fuel-gas spraying nozzles 11 a and 11 c spray thefuel gas toward the tangential direction of the inner circumferentialwall of the combustion chamber 10 at a high speed, and theoxygen-containing-gas spraying nozzles 11 b and 11 d spray theoxygen-containing-gas toward the tangential direction of the innercircumferential wall of the combustion chamber 10 at a high speed, so asto form a swirl while efficiently mixing the fuel gas and theoxygen-containing-gas at a region near the inner circumferential wall ofthe combustion chamber 10. The mixture gas forming such a swirl issuitably ignited by the ignition spark plug 21 so as to form atube-shaped flame within the combustion chamber 10. Note that acombustion gas is discharged from the front-end 10 a of the combustionchamber 10 a.

Note that the aforementioned oxygen-containing-gas represents a gas forcarrying oxygen used for combustion such as air, oxygen, oxygen-enrichedair, exhaust mixture gas, or the like.

With the present embodiment, the ignition spark plug 21 is disposed at aposition between the tube axis of the combustion chamber 10 and aposition away therefrom by r/2 (note that r denotes the radius of thecombustion chamber).

FIG. 3 shows the relation between the mounting position of the ignitionspark plug 21 along the radius direction of the combustion chamber 10and the ignition state using the ignition spark plug 21. Thisillustrates that the combustion chamber 10 including the ignition sparkplug 21 at a position between the tube axis and the position awaytherefrom by r/2 exhibits excellent ignition.

The reason why the flow speed of the swirl of the mixture gas of thefuel gas and the oxygen-containing-gas is relatively small near the tubeaxis of the combustion chamber 10, thereby effecting a mixture gas in asuitable range, and thereby enabling ignition definitely to be stable.

Thus, the tubular flame burner according to the present embodiment doesnot require any pilot burner for ignition, thereby reducing the size andcosts thereof.

Furthermore, in case that the tubular flame burner has a configuration,that is, a reduced distance L between each of the nozzles 11 a through11 d and the rear-end 10 b of the combustion chamber 10, in order tofurther reduce the size thereof, the distance L is insufficient formixing the fuel gas and the oxygen-containing-gas. Because, it leads toa problem that the region where gas fuel and oxygen-containing fuel aremixed in a suitable range of the air excess ratio may be reduced in theradius direction near the rear-end 10 b of the combustion chamber 10.Accordingly, the ignition spark plug 21 is preferably disposed at aposition between the tube axis and the position away therefrom by r/3.Thus, even in case of the tubular flame burner having such aconfiguration wherein the nozzles 11 a through 11 d are disposed closeto the ignition spark plug 21 (L≈0), excellent ignition can be done in adefinite way to be stable.

Note that while description has been made in the present embodimentregarding the arrangement wherein each of the fuel-gas spraying nozzlesand the oxygen-containing-gas spraying nozzles are disposed so that eachspraying direction matches with the tangential direction of the innercircumferential wall of the combustion chamber, an arrangement accordingto the present invention is not restricted to the arrangement whereineach spraying direction matches with the tangential direction thereof.It may be a case, an arrangement is made wherein each spraying directiondoes not match with the tangential direction of the innercircumferential wall of the combustion chamber as long as a swirl of thegas is formed within the combustion chamber.

Furthermore, while description has been made in the present embodimentregarding the arrangement wherein the slits serving as the nozzles forthe combustion chamber are disposed along the tube axis, and each slitis connected to the corresponding flat fuel-gas spraying nozzle oroxygen-containing spraying nozzle, an arrangement may be made, whereinmultiple small-sized openings forming a nozzle orifice for thecombustion chamber are formed along the tube axis, and each nozzle isconnected to the corresponding array formed of the small-sized openingsfor spraying the fuel gas or the oxygen-containing-gas.

Furthermore, description has been made in the present embodimentregarding the arrangement wherein the fuel gas is sprayed, anarrangement may be made wherein liquid fuel is sprayed. Note thatkerosene, gas oil, alcohol, A-type heavy oil, or the like, which readilyevaporates under relatively low temperature, is suitably employed as theliquid fuel.

Furthermore, description has been made in the present embodimentregarding the arrangement wherein the fuel gas and theoxygen-containing-gas are separately sprayed, an arrangement may be madewherein a mixture gas formed by premixing the fuel gas and theoxygen-containing-gas is sprayed.

In case of the tubular flame burner according to the present embodiment,the ignition spark plug is disposed at a suitable position near the tubeaxis of the combustion chamber, thereby performing ignition of a mixturegas of the fuel gas and the oxygen-containing-gas within the combustioncamber in a definite way to be stable. And furthermore, the tubularflame burner according to the present embodiment requires no ignitionpilot burner, thereby reducing the size and costs thereof.

Note that the tubular flame burner according to the present embodimentmay be also formed with a'polygonal cross-sectional shape rather thanround.

Second Embodiment Embodiment 2-1

Description will be made regarding a second embodiment of the presentinvention with reference to the drawings. FIG. 4 is a longitudinalcross-sectional diagram, which shows a tubular flame burner according tothe present embodiment.

The tubular flame burner comprises a combustion chamber 103 formed of aninner tube 101 of which one end opens, and an outer tube 102 whereinboth ends opens, and which can be slid along the outer circumferentialwall of the inner tube 101, a fuel-spraying nozzle 104 and anoxygen-containing-gas-spraying nozzle 105, wherein a nozzle orifice ofeach is formed on the inner face of the inner tube 101 of theaforementioned combustion chamber 103.

Note that the fuel-spraying nozzle 104 and theoxygen-containing-gas-spraying nozzle 105 are connected so that eachspraying direction generally matches the tangential direction of theinner circumferential wall of the combustion chamber 103 as viewed inthe diameter direction of the combustion chamber 103. Note that theoxygen-containing-gas represents a gas for carrying oxygen used forcombustion such as air, oxygen, oxygen-enriched air, exhaust mixturegas, or the like.

With such a configuration, the fuel is sprayed from the fuel-sprayingnozzle 104 into the combustion chamber 103 as well as spraying theoxygen-containing-gas from the oxygen-containing-gas-spraying nozzle105, and ignition is made by the ignition plug 106, whereby atube-shaped flame is formed along the inner circumferential wall of theinner tube 101 of the combustion chamber 103. The flame thus formed isreferred to as a tube-shaped flame 107.

While in general, a tubular flame burner is designed so that combustionof the tube-shaped flame 107 is made within the combustion chamber 103,with the tubular flame burner according to the present invention, a partof the tube-shaped flame 107 can be formed on the outside of the innertube 101, wherein in the event that the outer tube 102 is slid so as toextend the combustion chamber 103, the entire tube-shaped flame 107 isformed within the combustion chamber 103. And on the other hand, in theevent that the outer tube 102 is slid so as to collapse the combustionchamber 103, a part of the tube-shaped flame 107 is formed on theoutside of the combustion camber 103.

The lengths of the inner tube 101 and the outer tube 102 may beexperimentally determined as well as being theoretically determined.

With the entire length of the tube-shaped flame 107 thus formed as L₁,and with the length of the tube-shaped flame 107 formed on the outsideof the combustion chamber 103 as L₂, as shown in FIG. 5, the greater thevalue L₂/L₁ is, the greater the heat transfer amount and the amount ofcreated soot are, as shown in the chart in FIG. 6. The reason why isthat the increased L₂ causes an increase of the ratio of a luminousflame, and accordingly, the ratio of stable combustion is reduced withinthe combustion chamber 103 as well as promoting heat transfer to theheated object. This results in such a state that soot is readilygenerated.

On the other hand, the greater the L₂/L_(i) is, the smaller the amountof the created NOx as shown in the chart in FIG. 7. The reason why isthat increased ratio of combustion on the outside of the combustionchamber 103 within the furnace space leads to dilution-combustion whileswirling an exhaust gas within a space on the outside of the combustionchamber 103. Accordingly, the concentration of oxygen is reduced withinthe combustion space as well as preventing generation of partialhigh-temperature region, thereby suppressing reaction of creation ofthermal NOx, and thereby suppressing the amount of created NOx.

The tubular flame burner according to the present invention controls theheat transfer amount, the amount of created soot, and the amount of thecreated NOx.

Note that the tubular flame burner according to the present embodimentmay be also formed with a polygonal cross-sectional shape rather thanround.

Embodiment 2-2

Combustion testing was performed using the tubular flame burneraccording to the present invention.

FIG. 9 is a chart that shows the in-furnace temperature (curve A) andthe temperature of steel (curve B) over time, which have been measuredin the combustion test. In the aforementioned combustion test, thein-furnace temperature is raised at a constant temperature increase rateto 1000° C., and upon reaching 1000° C., the temperature is maintainedat 1000° C. for a total heating time of 15 hours.

First, steel was heated under the condition that the outercircumferential wall (denoted by reference numeral 102 in FIG. 4) wasslid toward the inside of the furnace such that L₂ shown in FIG. 5becomes 0 or less, i.e., the flame was formed only within the combustionchamber (first combustion test). FIG. 10 shows concentration of NOx andsoot over time obtained in the aforementioned combustion test.

In FIG. 10, an index representation of the concentration thereof isexpressed with the permissive value as 100.

In such a case, while only a small amount of soot was generated, theamount of NOx increased up to the concentration of index value 150 overtime until the in-furnace temperature reached 1000° C. And theconcentration of NOx was maintained to the high concentration of indexvalue 150 after the in-furnace temperature reached 1000° C. Accordingly,it has been revealed that the aforementioned combustion leads to aproblem of generating a high NOx.

On the other hand, the measured temperature of the steel after heatingfor 15 hours was 950° C., which was considerably lower than thedetermined temperature of 1000° C.

Next, steel was heated under the same conditions as the first combustiontest, except that the outer circumferential wall 102 was slid away fromthe inside of the furnace such that L₂ shown in FIG. 5 exceeds 0, i.e.,a part of the flame was formed outside the combustion chamber (thesecond combustion test). FIG. 11 shows the concentration of NOx and sootover time obtained in the aforementioned combustion test.

In FIG. 11, an index representation of the concentration is made withthe permissive values as 100. In the aforementioned combustion, while asomewhat great amount of soot was generated during thetemperature-rising step, the amount of the generated soot became smallafter the in-furnace temperature reached 1000° C., which brings up alittle bit problem. On the other hand, the amount of the generated NOxwas suppressed to a low level over all the heating steps. That is tosay, the combustion in such a case causes no problems to generate NOx,while leading to a small problem of a somewhat great amount of the sootgenerated in the temperature-rising step.

On the other hand, the measured temperature of the steel after heatingfor 15 hours was 980° C., which was closer to the determined temperatureof 1000° C., compared with the first combustion test. It has beenrevealed that the second combustion method exhibits more efficientheating of steel than with the first combustion method, except forgenerating the soot at a low temperature.

Next, steel was heated under the combination of heating conditions forthe first and second combustion test. This was done for the in-furnacetemperature to be as the same as the second combustion test, that is,after the in-furnace temperature exceeded 800° C., a part of the flamewas formed on the outside of the combustion chamber. This resulted insuppressing the amount of the generated soot and NOx to an extent of thepermissive values or less. These were done, based on the results fromthe first and second combustion tests (third combustion test).

FIG. 12 shows concentration of NOx and soot over time obtained in theaforementioned combustion test.

In FIG. 12, an index representation of the concentration thereof is madewith the permissive values as 100 in the same way. In the aforementionedcombustion, both the amount of the generated soot and that of thegenerated NOx exists in a stable condition, resulting in suppressing theconcentration values to low levels. In such a way, the amount of thegenerated soot is suppressed to an extent of the concentration value, 30or less. And the amount of the generated NOx is suppressed to an extentof the concentration value, 80 or less over all the heating steps,whereby excellent heating is achieved.

On the other hand, when the steel temperature was measured after heatedfor 15 hours, it was 975° C. And it has been revealed that efficientheating was achieved in the third combustion test, while the temperatureof steel was somewhat lower than that in the second combustion test.

As described above, it has been revealed that the combustion by a fixedand constant length of the combustion chamber of the tubular flameburner leads to a problem of generating soot at a low in-furnacetemperature. And it leads to a problem of generating NOx at a hightemperature therein. On the contrary, by adjusting the length of thecombustion chamber corresponding to the in-furnace temperature, thesteel can be heated in a good and an excellent way.

Third Embodiment Embodiment 3-1

FIG. 13 through FIG. 16 show a multi-stage tubular flame burneraccording to an embodiment of the present invention. FIG. 13 is a sideview of the multi-stage tubular flame burner according to the presentembodiment. FIG. 14A is a cross-sectional view taken line A-A in FIG.13. FIG. 14B is a cross-sectional view taken line B-B in FIG. 13. FIG.15 and FIG. 16 are explanatory diagrams, which describes a method forcontrolling combustion by the multi-stage tubular flame burner accordingto the present embodiment.

In FIG. 13, reference numeral 201 denotes the multi-stage tubular flameburner according to the present embodiment. FIG. 13 has such aconfiguration that a small-diameter flame burner 213 with a small innerdiameter is connected to the rear-end of a large-diameter flame burner202 with a large inner diameter in series, so as to form a singletubular flame burner.

The large-diameter tubular flame burner 202 includes a tubularcombustion chamber 210, whose one end 210 a opens for serving as anexhaust vent for a combustion gas, and nozzles 211 a, 211 b, 211 c, and211 d, for separately spraying a fuel gas and an oxygen-containing-gasinto the combustion chamber 210. Long and narrow slits 212 are formed atthe four parts. Here, the four parts are located on the same singlecircumference of the combustion chamber 210, and these slits are locatedat the neighborhood of the rear-end 210 b of the combustion chamber 210,in order to serve them as nozzle orifices for the combustion chamber210. And these slits 212 are connected to nozzles 211 a, 211 b, 211 c,and 211 d, as being formed flat, being long and narrow along the tubeaxis, respectively. The nozzles 211 a, 211 b, 211 c, and 211 d, aredisposed so that the spraying direction of each is in a tangentialdirection of the inner circumferential wall of the combustion chamber210, so as to cause a swirl in a single rotational direction. Of thesefour nozzles, two nozzles of the nozzles 211 a and 211 c serve asfuel-gas-spraying nozzles, and the rested two nozzles of these fournozzles, 211 b and 211 d serve as oxygen-containing-gas-sprayingnozzles.

The fuel-gas-spraying nozzles 211 a and 211 c spray a fuel gas in thetangential direction of the inner circumferential wall of the combustionchamber 210 at a high speed, as well as theoxygen-containing-gas-spraying nozzles 211 b and 211 d spraying anoxygen-containing-gas in the tangential direction of the innercircumferential wall of the combustion chamber 210 at a high speed, soas to form a swirl while efficiently mixing the fuel gas and theoxygen-containing-gas at a region near the inner circumferential wall ofthe combustion chamber 210. Upon ignition of the mixture gas forming aswirl by an ignition device (not shown) such as an ignition plug, pilotburner, or the like, a tube-shaped flame is formed within the combustionchamber 210. A combustion gas is discharged from the front-end 210 a ofthe combustion chamber 210.

On the other hand, as shown in FIG. 13 and FIG. 14B, the small-diametertubular flame burner 203 includes a tubular combustion chamber 213having a configuration. Here, the front-end 213 a is connected to therear-end 210 b of the large-diameter tubular flame burner 202, so as toserve as an exhaust vent for a combustion gas, and nozzles 214 a, 214 b,214 c, and 214 d, for separately spraying a fuel gas and anoxygen-containing-gas into the combustion chamber 213. Long and narrowslits 215 are formed at the respective four parts, on the same singlecircumference of the combustion chamber 213. They are located at theneighborhood of the rear-end 213 b of the combustion chamber 213 forserving as nozzle orifices for the combustion chamber 213. Here, theseslits 215 are connected to nozzles 214 a, 214 b, 214 c, and 214 d, asbeing flat, long and narrow along the tube axis, respectively. Therespective nozzles 214 a, 214 b, 214 c, and 214 d, are disposed so thatthe spraying direction of each is in a tangential direction of the innercircumferential wall of the combustion chamber 213, so as to cause aswirl in a single rotational direction. Of these four nozzles, twonozzles, 214 a and 214 c, serve as fuel-gas-spraying nozzles, and therested two nozzles of these nozzles, 214 b and 214 d, serve asoxygen-containing-gas-spraying nozzles.

Note that the slits 212 of the large-diameter tubular flame burner 202are formed with the area of each orifice larger than the slits 215 ofthe small-diameter tubular flame burner 203 corresponding to a largerinner diameter of the combustion chamber 210 of the large-diametertubular flame burner 202.

The fuel-gas-spraying nozzles 214 a and 214 c spray a fuel gas in thetangential direction of the inner circumferential wall of the combustionchamber 213 at a high speed, as well as theoxygen-containing-gas-spraying nozzles 214 b and 214 d spraying anoxygen-containing-gas in the tangential direction of the innercircumferential wall of the combustion chamber 213 at a high speed, soas to form a swirl while efficiently mixing the fuel gas and theoxygen-containing-gas at a region near the inner circumferential wall ofthe combustion chamber 213. Upon igniting the mixture gas forming aswirl by an ignition device (not shown) such as an ignition plug, pilotburner, or the like, a tube-shaped flame is formed within the combustionchamber 213. A combustion gas is discharged from the front-end 210 athrough the front-end 213 a of the combustion chamber 213 and thecombustion chamber 210 of the large-diameter tubular flame burner 202.

Note that the oxygen-containing-gas represents a gas for carrying oxygenused for combustion such as air, oxygen, oxygen-enriched air, exhaustmixture gas, or the like.

Furthermore, as shown in FIG. 15, an switching valve 216 a for switchingsupply of the fuel gas to the nozzles 211 a and 211 c is disposed at aportion on a line for supplying the fuel gas to the fuel-gas-sprayingnozzles 211 a and 211 c of the large-diameter tubular flame burner 202,and an switching valve 216 b for switching supply of theoxygen-containing-gas to the nozzles 211 b and 211 d is disposed at aportion on a line for supplying the oxygen-containing-gas to thefuel-gas-spraying nozzles 211 b and 211 d of the large-diameter tubularflame burner 202. Thus, switching is performed between use and stop ofthe large-diameter tubular flame burner 202 by switching the switchingvalves 216 a and 216 b.

Furthermore, an switching valve 217 a for switching supply of the fuelgas to the nozzles 214 a and 214 c is disposed at a portion on a linefor supplying the fuel gas to the fuel-gas-spraying nozzles 214 a and214 c of the small-diameter tubular flame burner 203, and an switchingvalve 217 b for switching supply of the oxygen-containing-gas to thenozzles 214 b and 214 d is disposed at a portion on a line for supplyingthe oxygen-containing-gas to the fuel-gas-spraying nozzles 214 b and 214d of the large-diameter tubular flame burner 203. Thus, switching isperformed between use and stop of the small-diameter tubular flameburner 203 by switching the switching valves 217 a and 217 b.

Furthermore, a supply controller 220 is provided for controlling on/offof the switching valves 216 a, 216 b, 217 a, 20 and 217 b, whereby thetubular flame burner to be used is selected for use by the on/offcontrol thereof.

Furthermore, a fuel-gas-flow regulator 218 for adjusting the total flowof the fuel gas to be supplied to the fuel-gas-spraying nozzles 211 a,211 c, 214 a, and 214 c, is disposed on a line for supplying the fuelgas, and an oxygen-containing-gas-flow regulator 219 for adjusting thetotal flow of the oxygen-containing-gas to be supplied to theoxygen-containing-gas-spraying nozzles 211 b, 211 d, 214 b, and 214 d,is disposed on a line for supplying the oxygen-containing-gas. Thesupply controller 220 controls the fuel-gas-flow regulator 218 and theoxygen-containing-gas-flow regulator 219 so as to control the total flowof supplied fuel gas and oxygen-containing-gas.

Note that the total supply flow of the fuel gas and theoxygen-containing-gas is measured by a flow-meter 221 for the fuel gasand a flow-meter 222 for the oxygen-containing-gas, and the measurementvalue is sent to the supply controller 220 so as to be used foradjusting the apertures of the fuel-gas-flow regulator 218 and theoxygen-containing-gas-flow regulator 219.

Description will be made below regarding a method for controllingcombustion by the multi-stage tubular flame burner 201 having such aconfiguration with reference to FIG. 15 and FIG. 16.

With the combustion control method for the multi-stage tubular flameburner, a desired tubular flame burner is selected for combustion fromthe large-diameter tubular flame burner 202 and the small-diametertubular flame burner 203 corresponding to the combustion load.

That is to say, each of the large-diameter tubular flame burner 202 andthe small-diameter tubular flame burner 203 has a particular possiblerange of combustion. That is, a particular range of the combustion load,corresponding to the range of supply flow between the minimalflame-formation flow speed required for forming a tubular flame and themaximal permissive flow speed dependent upon the pressure loss. Here,the small-diameter tubular flame burner 203 is formed with a small innerdiameter of the combustion chamber and a small aperture area of theslits. Accordingly, it has a possible range of combustion correspondingto a range of a small combustion load, and on the other hand, thelarge-diameter tubular flame burner 202 is formed with a large innerdiameter of the combustion chamber and a large aperture area of theslits, and accordingly has a possible range of combustion correspondingto a range of a relatively large combustion load.

Thus, in case of a small combustion load, the small-diameter tubularflame burner 203 is used. And in the event that the combustion loadbecomes greater, the large-diameter tubular flame burner 202 is used.And in the event that the combustion load becomes much greater, both thelarge-diameter tubular flame burner 202 and the small-diameter tubularflame burner 203 are used.

Thus, the multi-stage tubular flame burner according to the presentembodiment enables stable combustion to be in a wide range of thecombustion load, which is difficult for a single-diameter tubular flameburner.

Note that the tubular flame burner according to the present embodimentmay also be formed with a polygonal cross-sectional shape, rather thanround.

Embodiment 3-2

Next, description will be made regarding another embodiment withreference to FIG. 17.

In the previous embodiment, as shown in FIG. 15, the multi-stage tubularflame burner has a configuration for adjusting the total flow of thefuel gas and the total flow of the oxygen-containing-gas to be suppliedto the tubular flame burner that has a large diameter, and/or thetubular flame burner that has a small-diameter. An arrangement accordingto the present embodiment has a configuration for further adjusting thetotal flow of the fuel gas and the total flow of theoxygen-containing-gas to be supplied for each of the large-diametertubular flame burner 210 and the small-diameter tubular flame burner213.

That is to say, as shown in FIG. 17, first, a fuel-gas-flow regulator218 a for adjusting the flow of the fuel gas to be supplied to thefuel-gas-spraying nozzles 211 a and 211 c is provided on a line forsupplying the fuel gas to the tubular flame burner 210 that has alarge-diameter, and furthermore, an oxygen-containing-gas-flow regulator219 a for adjusting the flow of the oxygen-containing-gas to be suppliedto the oxygen-containing-gas-spraying nozzles 211 b and 211 d isprovided on a line for supplying the oxygen-containing-gas to thetubular flame burner that has a large-diameter 210. The supplycontroller 220 a adjusts the fuel-gas-flow regulator 218 a and theoxygen-gas-flow regulator 219 a, so as to control each of the fuel-gasflow and the oxygen-containing-gas flow to be supplied to thelarge-diameter tubular flame burner. The supply flow of the fuel gas andthe supply flow of the oxygen-containing-gas are measured by a fuel-gasflow-meter 221 a and an oxygen-containing-gas flow-meter 222 a,respectively. And the measurement values are sent to the supplycontroller 220 a, so as to be used for aperture adjustment of thefuel-gas-flow regulator 218 a and the oxygen-containing-gas-flowregulator 219 a.

In the same way, a fuel-gas-flow regulator 218 b for adjusting the flowof the fuel gas to be supplied to the fuel-gas-spraying nozzles 214 aand 214 c is provided on a line for supplying the fuel gas to thesmall-diameter tubular flame burner 213. And furthermore, anoxygen-containing-gas-flow regulator 219 b for adjusting the flow of theoxygen-containing-gas to be supplied to theoxygen-containing-gas-spraying nozzles 214 b and 214 d is provided on aline for supplying the oxygen-containing-gas to the small-diametertubular flame burner 213. The supply controller 220 b adjusts thefuel-gas-flow regulator 218 b and the oxygen-gas-flow regulator 219 b,so as to control each of the fuel-gas flow and the oxygen-containing-gasflow to be supplied to the small-diameter tubular flame burner 213. Thesupply flow of the fuel gas and the supply flow of theoxygen-containing-gas are measured by a fuel-gas flow-meter 221 b and anoxygen-containing-gas flow-meter 222 b, respectively. And themeasurement values are sent to the supply controller 220 b so as to beused for aperture adjustment of the fuel-gas-flow regulator 218 b andthe oxygen-containing-gas-flow regulator 219 b.

The supply controller 220 a for the large-diameter tubular flame burner210 and the supply controller b for the small-diameter tubular flameburner 213 are interconnected each other for adjusting the total supplyflow of the fuel gas and the oxygen-containing-gas.

In case of a small combustion load, using the multi-stage tubular flameburner having such a configuration and doing the combustion, each of theapertures are adjusted corresponding to the combustion state. (Here,each of the apertures exists between the fuel-gas-flow regulator 218 band the oxygen-containing-gas-flow regulator 219 b of the tubular flameburner 213 that has the small diameter. Here, each of the apertures isdetermined and adjusted to be zero, wherein the respective aperturesexist between the fuel-gas-flow regulator 218 a and theoxygen-containing-gas-flow regulator 219 a of the tubular flame burner210 that has a large-diameter. And, in the event that the combustionload becomes greater, each of the apertures of the fuel-gas-flowregulator 218 a and the oxygen-containing-gas-flow regulator 219 a ofthe large-diameter tubular flame burner 210 are adjusted correspondingto the combustion state. In this case, each of the apertures of thefuel-gas-flow regulator 218 b is set to be zero, wherein each of theapertures exist between the oxygen-containing-gas-flow regulator 219 bof the small-diameter tubular flame burner 213. Furthermore, in theevent that the combustion load becomes more greater, the apertures ofthe fuel-gas-flow regulator 218 b and the oxygen-containing-gas-flowregulator 219 b of the small-diameter tubular flame burner 213, whichhave been determined to be zero, open. The fuel-gas-flow regulator 219 bof the large-diameter tubular flame burner 210 opens corresponding tothe combustion load. And concerning the apertures of the fuel-gas-flowregulator 218 a and the oxygen-containing-gas-flow regulator 219 a ofthe large-diameter tubular flame burner 210 and the apertures of thefuel-gas-flow regulator 218 b and the oxygen-containing-gas-flowregulator 219 b of the small-diameter tubular flame burner 213, they areas follows. That is, both of the apertures are adjusted respectively,corresponding to the combustion load.

Thus, the multi-stage tubular flame burner according to the presentembodiment enables stable combustion to exist within a wide range of thecombustion load, which is hard to be applied to a single-diametertubular flame burner.

Up to now, in the above-described embodiments, description has been maderegarding the arrangement that has a configuration so that two tubularflame burners are connected. But, it may be a case, another arrangementis made to have a configuration, wherein three or more tubular flameburners are connected, in accordance with the respective requirements.

Furthermore, description has been made in the above-describedembodiments regarding the arrangement, wherein the fuel-gas-sprayingnozzles and the oxygen-containing-gas-spraying nozzles are disposed sothat each spraying direction is in a tangential direction of the innercircumferential wall of the combustion chamber. However, an arrangementaccording to the present invention is not always applied to theaforementioned one. It may be a case, an arrangement is applied to thatany spraying direction is not in a tangential direction of the innercircumferential wall of the combustion chamber as long as a swirl of amixture gas is formed within the combustion chamber.

Furthermore, description has been made in the above-describedembodiments regarding the arrangement, wherein the slits serving as thenozzles for the combustion chamber are disposed along the tube axis, andwherein each slit is connected to the corresponding flat fuel-gasspraying nozzle or oxygen-containing spraying nozzle. But, it may be acase, an arrangement is applied to that multiple small-sized openings,which serve as a nozzle orifice for the combustion chamber, are formedalong the tube axis. And, it may be a case, each nozzle is connected tothe corresponding array formed of the small-sized openings for sprayingthe fuel gas or the oxygen-containing-gas.

Furthermore, description has been made in the present embodimentregarding the arrangement, wherein the fuel gas and theoxygen-containing-gas are separately sprayed.

However, it may be a case, an arrangement is applied to another way,that is, a mixture gas formed by premixing the fuel gas and theoxygen-containing-gas is sprayed.

According to the present embodiment, when the multi-stage tubular flameburner is used, a suitable tubular flame burner is used selectively forcombustion corresponding to the variable increasing/decreasingcombustion load, resulting in making it possible to keep a stablecombustion in accordance with a wide range of the combustion load.

The tubular flame burner according to the present embodiment may also beformed with a polygonal cross-sectional shape, rather than round.

Fourth Embodiment

Description is made regarding to a tubular flame burner according to thefourth embodiment of the present invention, referencing to the drawings.FIG. 18A is a configuration diagram of the tubular flame burner, andFIG. 18B is a view taken along line B-B in FIG. 18A.

The tubular flame burner includes a tubular combustion chamber 301 whoseone-end opens and nozzles 304 for spraying a fuel gas and anoxygen-containing-gas. Here, each nozzle orifice of the nozzles isformed on the inner face of the aforementioned combustion chamber 301.It is disposed so that each spraying direction is in a neighborhood of atangential direction of the inner circumferential wall of such aconfiguration that the combustion chamber 301 is combustion chamber 301.And the tubular flame burner has covered with an outer tube 302, whichhas a greater outer diameter than that of the combustion chamber 301.This is as a role to form a space between the outer face of thecombustion chamber 301 and the inner face of the outer tube 302. Here,the space between the outer face and the inner face serves as a flowpath 303 for a fuel gas or an oxygen-containing-gas. The path isprovided before being supplied to the aforementioned spraying nozzle, aswell as forming the combustion chamber 301 with a greater length thanthat of a tube-shaped flame formed therein.

One end of the combustion chamber 301 opens for serving as an exhaustvent for a combustion exhaust gas. Furthermore, long slits are formed onthe other end of the combustion chamber 301 along the tube axis, and areconnected to nozzles 304 for separately spraying the fuel gas and theoxygen-containing-gas.

The nozzles 304 are disposed in a neighborhood of a tangential directionof the inner circumferential wall of the combustion chamber 301, so asto form a swirl within the combustion chamber 301 due to spraying of thefuel gas and the oxygen-containing-gas. Note that the tip of each nozzle304 is formed flat with a reduced orifice area so as to spray the fuelgas and the oxygen-containing-gas at a high speed. Reference numeral 305denotes an ignition plug.

The outer tube 302 has closed front-end and rear-one. And the outer tubehas a configuration, wherein a pipe 306 is connected to a portion on thefront-end side of the outer tube 302 for supplying a combustion gas oran oxygen-containing-gas to a space 303 formed between the combustioncamber 301 and the outer tube 302.

On the other hand, a pipe 307, connected to one of the aforementionednozzle 304, is connected to a portion on the rear-end side of the outertube 302, so as to introduce the preheated fuel gas oroxygen-containing-gas to the nozzle 304. In such a case, when thepreheated fuel gas is supplied, the oxygen-containing-gas before havingbeen preheated is supplied to the other nozzle 304 that is disposedthereon. On the other hand, when the preheated oxygen-containing-gas issupplied, the fuel gas before having been preheated is supplied to theother nozzle 304 that is disposed thereon.

The tubular flame burner, according to the present embodiment, has thesame configuration as the conventional tubular flame burners, except forthe above-described configuration, wherein the fuel gas or theoxygen-containing-gas is preheated, so as to be supplied to thecombustion chamber 301. And the tubular flame burner has the samecombustion mechanism as the conventional tubular flame burners.Accordingly, detailed description thereof is omitted.

The tubular flame burner according to the present embodiment is formedso that the combustion chamber is longer than a tube-shaped flame formedtherewithin. Accordingly, while the front-end of the combustion chamberbecomes high temperature due to the combustion gas, the fuel gas oroxygen-containing-gas that has a room temperature cools the combustionchamber. Accordingly, the burner is not damaged due to heat, therebyimproving the life span of the burner. Furthermore, with the tubularflame burner according to the present embodiment, the fuel gas oroxygen-containing-gas is preheated, thereby improving combustionperformance, and thereby extending a range of kinds of fuel, which canbe employed for combustion.

Note that the tubular flame burner according to the present embodimentmay also be formed with a polygonal cross-sectional shape rather thanround.

EXAMPLES

In order to confirm the effectiveness of the double-tube burneraccording to the present embodiment, combustion test was performed,using fuel that has a low calorific heating value. Note that combustiontest was also performed using a conventional single-tube tubular flameburner as a comparative example (without preheating of the combustionair or fuel). A mixture gas formed of only a blast furnace gas or formedby mixing the blast furnace gas (BFG) with N₂ gas or a coke-oven gas(COG) is employed as the aforementioned fuel gas that has a lowercalorific heating value than that of the blast furnace gas. Table 1shows the obtained results.

Note that the fuel gases having the same components were employed in thecomparative examples 1 through 3 as in the present examples in Table 1.

TABLE 1 BFG N2 COG Air amount amount amount amount Theoretical Airexcess Nm³/h Nm³/h Nm³/h Nm³/h air amount ratio Present 1 36.3 — — 35.30.752 1.29 examples 2 9.9 20.7 1.5 26.9 0.455 1.84 3 15.3 10.2 — 12.90.451 1.12 4 15.2 — — 13.7 0.752 1.20 5 15.0 10.0 — 13.2 0.451 1.17Comparative 1 36.3 — — 35.3 0.752 1.29 examples 2 9.9 20.7 1.5 26.90.455 1.84 3 15.3 10.2 — 12.9 0.451 1.12 Preheating Heat temperature (°C.) amount Preheating Air for Combustion of fuel of fuel or aircombustion Fuel state Present 1 933 Yes 363 Room Good examplestemperature 2 504 Yes 272 Room Good temperature 3 560 Yes 270 Room Goodtemperature 4 933 Yes Room 263 Good temperature 5 560 Yes Room 143 Goodtemperature Comparative 1 933 No Room Room Good examples temperaturetemperature 2 504 No Room Room unsatisfactory temperature temperature 3560 No Room Room unsatisfactory temperature temperature Note: CalorificValue (Heating value) is represented by “kcal/Nm³”

As can be clearly understood from Table 1, in case of combustion of theblast furnace gas, excellent combustion was obtained both in the presentexample wherein the combustion air has been preheated, and thecomparative example 1 wherein the combustion air has not been preheated.But, on the other hand, in case of combustion of a fuel gas with lowerheating value than with the blast furnace gas, poor combustion occurredin the comparative examples 2 and 3, wherein the combustion air and thefuel gas have not been preheated. On the contrary, excellent combustionwas obtained in the present examples 2 through 5, wherein the combustionair or the fuel gas has been preheated.

Note that examples of the fuel gases with low heat output used in thepresent examples 2 and 3 include an exhaust gas from a reducingatmosphere furnace or a non-oxidizing atmosphere furnace. Such anuntreated exhaust gas cannot be discharged prohibited. Therefore, theexhaust gas is burned with a dedicated combustion furnace so as to bedischarged into the air. From such a viewpoint, the present embodimenthas such an advantage that double-tube tubular flame furnace enablescombustion to be made using such an exhaust gas as a fuel gas withoutrequiring a special dedicated combustion furnace.

Fifth Embodiment Embodiment 5-1

FIG. 19 through FIG. 22 show an embodiment 5-1 according to the presentinvention. FIG. 19 is a side view of a tubular flame burner according tothe present embodiment,

FIG. 20A is a cross-sectional view taken along line A-A in FIG. 19, andFIG. 20B is a cross-sectional view taken along line B-B in FIG. 19. FIG.21 is an overall configuration diagram of a combustion controller forthe tubular flame burner according to the present embodiment, and FIG.22 is an explanatory diagram for describing a combustion control methodfor the tubular flame burner according to the present embodiment.

In FIG. 19, reference numeral 410 denotes a tube-shaped combustionchamber, wherein the front-end 410 a opens so as to serve as an exhaustvent for a combustion exhaust gas. Furthermore, the combustion chamber410 includes two nozzle-mounting portions A and B on the side of therear-end 410 b along the tube axis for mounting nozzles for spraying afuel gas to the combustion chamber 410, and nozzles for spraying anoxygen-containing-gas thereto.

At the nozzle-mounting portion A, four long and narrow slits 412extending along the tube axis are formed along the circumferential wallof the combustion chamber 410 so as to serve as nozzles for thecombustion chamber 410. And these slits are connected to nozzles 411 a,411 b, 411 c, and 411 d, formed flat, and long and narrow along the tubeaxis, respectively, as shown in FIG. 19 and FIG. 20A. The nozzles 411 a,411 b, 411 c, and 411 d, are disposed so that each spraying direction isin a tangential direction of the inner circumferential wall of thecombustion chamber 410 so as to cause a swirl to be in a predeterminedrotational direction. Of these four nozzles, the nozzle 411 a and thenozzle 411 c serve as fuel-gas-spraying nozzles, and the nozzle 411 band the nozzle 411 d serve as oxygen-containing-gas spraying nozzles.

The fuel gas is sprayed from the fuel-gas spraying nozzles 411 a and 411c in the tangential direction of the inner circumferential wall of thecombustion chamber 410 at a high speed. Such a procedure is as well asspraying the oxygen-containing-gas from the oxygen-containing-gasspraying nozzles 411 b and 411 d in the tangential direction of theinner circumferential wall of the combustion chamber 410 at a highspeed. This results in forming a swirl while efficiently mixing the fuelgas and the oxygen-containing-gas at a region near the innercircumferential wall of the combustion chamber 410. Upon ignition of themixture gas forming a swirl by an ignition device (not shown) such as anignition plug, pilot burner, or the like, a tube-shaped flame is formedwithin the combustion chamber 410.

In the same way, at the nozzle-mounting portion B, four long and narrowslits 414 extending along the tube axis are formed along thecircumferential wall of the combustion chamber 410 so as to serve asnozzles for the combustion chamber 410. These nozzles are connected tonozzles 413 a, 413 b, 413 c, and 413 d, formed flat, and long and narrowalong the tube axis, respectively, as shown in FIG. 19 and FIG. 20B. Thenozzles 413 a, 413 b, 413 c, and 413 d, are disposed so that eachspraying direction is in a tangential direction of the innercircumferential wall of the combustion chamber 410 so as to cause aswirl to be in a predetermined rotational direction. Of these fournozzles, the nozzle 413 a and the nozzle 413 c serve asfuel-gas-spraying nozzles, and the nozzle 413 b and the nozzle 413 dserve as oxygen-containing-gas spraying nozzles.

The fuel gas is sprayed from the fuel-gas spraying nozzles 413 a and 413c in the tangential direction of the inner circumferential wall of thecombustion chamber 410 at a high speed. This procedure is done as wellas spraying the oxygen-containing-gas from the oxygen-containing-gasspraying nozzles 413 b and 413 d in the tangential direction of theinner circumferential wall of the combustion chamber 410 at a highspeed, so as to form a swirl while efficiently mixing the fuel gas andthe oxygen-containing-gas at a region near the inner circumferentialwall of the combustion chamber 410. Upon ignition of the mixture gasforming a swirl by an ignition device (not shown) such as an ignitionplug, pilot burner, or the like, a tube-shaped flame is formed withinthe combustion chamber 410.

As described above, the tubular flame burner according to the presentembodiment includes two nozzle sets along the tube axis. Each of theseones are formed of two fuel-gas-spraying nozzles and twooxygen-containing-gas spraying nozzles along the circumference of thetube, i.e., the tubular flame burner according to the present embodimentincludes four fuel-gas-spraying nozzles and four oxygen-containing-gasspraying nozzles.

Note that the oxygen-containing-gas represents a gas for carrying oxygenused for combustion such as air, oxygen, oxygen-enriched air, exhaustmixture gas, or the like.

Furthermore, as shown in FIG. 20, switching valves 415 a, 415 c, 416 a,and 416 c, for controlling on/off of the fuel gas to the nozzles 411 a,411 c, 413 a, and 413 c, respectively, are disposed on lines forsupplying the fuel gas to the fuel-gas spraying nozzles 411 a, 411 c,413 a, and 413 c, respectively. And switching valves 415 b, 415 d, 416b, and 416 d, for controlling on/off of the oxygen-containing-gas to thenozzles 411 b, 411 d, 413 b, and 413 d, respectively, are disposed onlines for supplying the oxygen-containing-gas to theoxygen-containing-gas spraying nozzles 411 b, 411 d, 413 b, and 413 d,respectively.

Furthermore, a supply controller 420 is provided for controlling on/offof the switching valves 415 a, 415 b, 415 c, 415 d, 416 a, 416 b, 416 c,and 416 d, so as to select desired nozzles for spraying the fuel gas andthe oxygen-containing-gas to the combustion chamber 410.

Furthermore, the line for supplying the fuel gas includes afuel-gas-flow regulator 417 for adjusting the total supply flow of thefuel gas to be supplied to the fuel-gas-spraying nozzles 411 a, 411 c,413 a, and 413 c, and on the other hand, the line for supplying theoxygen-containing-gas includes an oxygen-containing-gas-flow regulator418 for adjusting the total supply flow of the oxygen-containing-gas tobe supplied to the oxygen-containing-gas-spraying nozzles 411 b, 411 d,413 b, and 413 d. The supply controller 420 adjusts the fuel-gas-flowregulator 417 and the oxygen-containing-gas-flow regulator 418 so as tocontrol each entire flow of the fuel gas and the oxygen-containing-gasto be supplied according to the combustion load. That is to say, in caseof small combustion load, the apertures of the fuel-gas-flow regulator417 and the oxygen-containing-gas-flow regulator 418 are reduced so asto reduce the total supply flow thereof. And on the other hand, in caseof a great combustion load, the apertures of the fuel-gas-flow regulator417 and the oxygen-containing-gas-flow regulator 418 are increased so asto increase the total supply flow thereof.

A fuel-gas flow-meter 421 and an oxygen-containing-gas flow-meter 422measure each of total supply flow of the fuel gas and theoxygen-containing-gas. And the measured values are sent to the supplycontroller 420 so as to be used for adjusting the apertures of thefuel-gas-flow regulator 417 and the oxygen-containing-gas-flow regulator418.

Description will be made regarding a combustion control method for thetubular flame burner using the combustion controller having such aconfiguration with reference to FIG. 21 and FIG. 22.

In the method for controlling the combustion by the tubular flameburner, the number of nozzles used for spraying the fuel gas and theoxygen-containing-gas to the combustion chamber 410 is determinedaccording to the combustion load so that the fuel gas and theoxygen-containing-gas are sprayed at an initial flow speed in a rangebetween the maximal permissive flow speed Vp dependent upon the pressureloss and the minimal flow speed Vq required for forming a tube-shapedflame.

That is to say, when increasing each total supply flow of the fuel gasand the oxygen-containing-gas sprayed to the combustion chamber 410according to the combustion load, in case that the switching valve 415 aopens while closing the other three switching valves 415 c, 416 a, and416 c, for spraying the fuel gas from only the fuel-gas-spraying nozzle411 a, and the switching valve 415 b opens while closing the other threeswitching valves 415 d, 416 b, and 416 d, for spraying theoxygen-containing-gas from only the oxygen-containing-gas-sprayingnozzle 411 b, all the supplied fuel gas flow is concentrated at thesingle fuel-gas spraying nozzle 411 a while concentrating all thesupplied oxygen-containing-gas flow at the singleoxygen-containing-gas-spraying nozzle 411 b, and accordingly, theinitial flow speed from the spraying nozzles 411 a and 411 b is rapidlyincreased over the increased total supply flow, i.e., increasedcombustion load, as shown by the line L₁ in FIG. 22A. As a result, whilethe flow speed rapidly reaches the minimal flow speed Vq required forforming a tube-shaped flame, the flow speed rapidly exceeds the maximalpermissive flow speed Vp dependent upon the pressure loss.

On the other hand, in case that the two switching valves 415 a and 415 copen while closing the other two switching valves 416 a, and 416 c, forspraying the fuel gas from the two fuel-gas-spraying nozzles 411 a and411 c, and in case that the switching valves 415 b and 415 d open whileclosing the other two switching valves 416 b and 416 d, for spraying theoxygen-containing-gas from the two oxygen-containing-gas-spraying nozzle411 b and 411 d, the supplied fuel gas flow is divided into two halvesso as to be sprayed from the two fuel-gas spraying nozzles 411 a and 411c, respectively, and the supplied oxygen-containing-gas flow is dividedinto two halves so as to be sprayed from the two oxygen-containing-gasspraying nozzles 411 b and 411 d, respectively. Accordingly, the initialflow speed from the spraying nozzles relatively gently increase over theincreased total supply flow, i.e., increased combustion load, as shownby the line L₂ in FIG. 22A. Specifically, in this case, the flow speedincreases over the combustion load with a half ratio as compared with acase of using a single nozzle 411 a for spraying the fuel gas and asingle nozzle 411 b for spraying the oxygen-containing-gas. As a result,while the flow speed relatively slowly reaches the minimal flow speed Vqrequired for forming a tube-shaped flame, the flow speed relativelyslowly exceeds the maximal permissive flow speed Vp dependent upon thepressure loss.

Furthermore, in a case that all the four switching valves 415 a, 415 c,416 a, and 416 c, open for spraying the fuel gas from the fourfuel-gas-spraying nozzles 411 a, 411 c, 413 a, and 413 c, while openingall the four switching valves 415 b, 415 d, 416 b, ad 416 d, forspraying the oxygen-containing-gas from the fouroxygen-containing-gas-spraying nozzle 411 b, 411 d, 413 b, and 413 d,the supplied fuel gas flow is divided into four quarters so as to besprayed from the four fuel-gas spraying nozzles 411 a, 411 c, 413 a, and413 c, respectively, and the supplied oxygen-containing-gas flow isdivided into four quarters so as to be sprayed from the fouroxygen-containing-gas spraying nozzles 411 b, 411 d, 413 b, and 413 d,respectively. Accordingly, the initial flow speed from the sprayingnozzles extremely gently increases over the increased total supply flow,i.e., the increased combustion load as shown by the line L₃ in FIG. 17A.Specifically, in this case, the flow speed increases over the combustionload with a quarter ratio as compared with a case of using a singlenozzle 411 a for spraying the fuel gas and a single nozzle 411 b forspraying the oxygen-containing-gas. As a result, while the flow speedconsiderably slowly reaches the minimal flow speed Vq required forforming a tube-shaped flame, the flow speed considerably slowly exceedsthe maximal permissive flow speed Vp dependent upon the pressure loss.

Based on the above-described relation, the present combustion controlmethod determines that the number of the nozzles to be used for sprayingthe fuel gas and the oxygen-containing-gas is adjusted by the supplycontroller 420, which controls on/off of the switching valves 415 a, 415b, 415 c, 415 d, 416 a, 416 b, 416 c, and 416 d. Such a determination isdone, in order for the fuel gas and the oxygen-containing-gas to besprayed into the combustion chamber 410, at an initial flow speed withina range of the maximal permissive flow speed Vp and the minimal flowspeed Vq. Here, Vp is dependent upon the pressure loss, and Vq isrequired for forming a tube-shaped flame. Specifically, as shown in FIG.22B, when a combustion load is fallen within a range from thepredetermined minimal combustion load to that of approximately ¼ of thepredetermined maximum combustion load, a single nozzle for spraying thefuel gas and a single nozzle for spraying the oxygen-containing-gas areused. When a combustion load is fallen within a range from aapproximately ¼ of the predetermined maximum combustion load toapproximately ½ of the predetermined maximum combustion load, twonozzles for spraying the fuel gas and two nozzles for spraying theoxygen-containing-gas are used. Furthermore, in case of a combustionload in a range between a load of approximately ½ to the predeterminedmaximal combustion load, four nozzles for spraying the fuel gas and fournozzles for spraying the oxygen-containing-gas are used.

Thus, as shown by the line M in FIG. 22A, the initial flow speed fromthe spraying nozzles is obtained within a range between the maximalpermissive flow speed Vp (Vp is dependent on the pressure loss), and theminimal flow speed Vq (Vp is required for forming a tube-shaped flame).Such a procedure results in suppressing excessive pressure loss, whilemaintaining the high speed of the flow required for forming atube-shaped flame.

As described above, the tubular flame burner according to the presentembodiment includes two nozzles that set along the tube axis. Each ofthese nozzles is formed of two fuel-gas-spraying nozzles and twooxygen-containing-gas-spraying nozzles along a single circumference ofthe tubular combustion chamber 410. These nozzles have such aconfiguration that the nozzles to be used for combustion are selectedfrom the multiple fuel-gas spraying nozzles and theoxygen-containing-gas spraying nozzles. These nozzles are used byappropriately controlling on/off of the switching values, so as toexhibit a predetermined flow speed, even in case of change in the totalsupply flow of the fuel gas and the oxygen-containing-gas, correspondingto change in the combustion load. This results in suppressing thepressure loss at the time of an increase of the supply flow, as well asmaintaining formation of a swirl at the time of reduction of the supplyflow.

Note that while description has been made in the present embodimentregarding the tubular flame burner including two nozzle sets along thetube axis, each of which are formed of two fuel-gas spraying nozzles andtwo oxygen-containing-gas spraying nozzles along a single circumferencethereof, the tubular flame burner may include a suitable number ofnozzle sets along the tube axis, each of which are formed of a suitablenumber of fuel-gas spraying nozzles and two oxygen-containing-gasspraying nozzles along a single circumference thereof, as appropriate.

Furthermore, description has been made in the present embodimentregarding another arrangement. That is, the fuel-gas-spraying nozzlesand the oxygen-containing-gas-spraying nozzles are disposed so that eachspraying direction is in a tangential direction of the innercircumferential wall of the combustion chamber. The arrangementaccording to the present invention is not restricted to theaforementioned arrangement. It may be a case, any spraying direction isnot in a tangential direction of the inner circumferential wall of thecombustion chamber as long as a swirl of a mixture gas is formed withinthe combustion chamber.

Furthermore, description has been made in the present embodimentregarding another arrangement. It may be a case, that the slits servingas the nozzles for the combustion chamber are disposed along the tubeaxis. And each slit is connected to the corresponding flat fuel-gasspraying nozzle or oxygen-containing spraying nozzle. An arrangement maybe made, wherein multiple small-sized openings serving as a nozzleorifice for the combustion chamber are formed along the tube axis. Andeach nozzle is connected to the corresponding array formed of thesmall-sized openings for spraying the fuel gas or theoxygen-containing-gas.

Furthermore, description has been made in the present embodimentregarding another arrangement, wherein the fuel gas is sprayed, butliquid fuel may be sprayed. It may be a case, liquid fuel which readilyevaporate under relatively low temperature, such as kerosene, gas oil,alcohol, A-type heave oil, or the like, is suitably employed as theliquid fuel.

Note that the tubular flame burner according to the present embodimentmay also be formed with a polygonal cross-sectional shape rather thanround.

Embodiment 5-2

The present embodiment is shown in FIG. 26. FIG. 26 is an overallconfiguration diagram, which shows a combustion controller for a tubularflame burner according to the present embodiment.

The combustion controller, according to the above-described embodiment5-1, has such a configuration as the total flow of the fuel gas and thetotal flow of the oxygen-containing-gas. Here, they are supplied to thenozzles at the mounting portion A and/or the nozzles at the mountingportion B are adjusted, as shown in FIG. 21. The combustion controlleraccording to the present embodiment has a configuration wherein thefuel-gas flow and the oxygen-containing-gas flow to be supplied to thenozzles mounted on the mounting portion A are independently adjusted.

That is to say, as shown in FIG. 26, the line for supplying the fuel gasto the nozzles at the mounting portion A includes a fuel-gas-flowregulator 417 a for controlling the fuel-gas flow to be supplied to thefuel-gas spraying nozzles 411 a and 411 c. On the other hand, the linefor supplying the oxygen-containing-gas to the nozzles at the mountingportion A includes an oxygen-containing-gas-flow regulator 418 a forcontrolling the oxygen-containing-gas flow to be supplied to theoxygen-containing-gas spraying nozzles 411 b and 411 d. Thefuel-gas-flow regulator 417 a and the oxygen-containing-gas-flowregulator 418 a are controlled by the supply controller, therebyenabling the fuel gas flow and the oxygen-containing-gas flow to beadjusted in order to be supplied to the nozzles at the mounting portionA. The flow-meter 421 a for the fuel gas and the flow-meter 422 a forthe oxygen-containing-gas measure the supply amounts of the fuel gas andthe oxygen-containing-gas, respectively. And the measured values aresent to the supply controller 420 a so as to be used for adjusting theapertures of the fuel-gas-flow regulator 417 a and theoxygen-containing-gas-flow regulator 418 a. In the same way, the linefor supplying the fuel gas to the nozzles at the mounting portion Bincludes a fuel-gas-flow regulator 417 b for controlling the fuel-gasflow to be supplied to the fuel-gas spraying nozzles 413 a and 413 c. Onthe other hand, the line for supplying the oxygen-containing-gas to thenozzles at the mounting portion B includes an oxygen-containing-gas-flowregulator 418 b for controlling the oxygen-containing-gas flow to besupplied to the oxygen-containing-gas spraying nozzles 413 b and 413 d.The supply controller 420 b controls the fuel-gas-flow regulator 417 band the oxygen-containing-gas-flow regulator 418 b. The supply amountsof the fuel gas and the oxygen-containing-gas to be supplied to thenozzles at the mounting portion B are measured by the flow-meter 421 bfor the fuel gas, and the flow-meter 422 b for theoxygen-containing-gas, respectively. The measured values are sent to thesupply controller 420 b so as to be used for adjusting the apertures ofthe fuel-gas-flow regulator 417 b and the oxygen-containing-gas-flowregulator 418 b.

The supply controller 420 a for the nozzles at the mounting portion Aand the supply controller 420 b for the nozzles at the mounting portionB, are interconnected each other for adjusting the total supply flow ofthe fuel gas and the oxygen-containing-gas.

Furthermore, switching valves 415 a and 415 c are provided forcontrolling on/off of the supply of the fuel gas to the fuel-gasspraying nozzles 411 a and 411 c at the mounting portion A. On the otherhand, the line for supplying the oxygen-containing-gas to theoxygen-containing-gas spraying nozzles 411 b and 411 d at the mountingportion A includes switching valves 415 b and 415 d for controllingon/off of supply of the oxygen-containing-gas to the nozzles 411 b and411 d, respectively. Here, each of the switching valves 415 a, 415 b,415 c, and 415 d, are controlled by the supply controller 420 a.

On the other hand, the aforementioned line for supplying the fuel gas tothe fuel-gas spraying nozzles 413 a and 413 c at the mounting portion Bincludes switching valves 416 a and 416 c for controlling on/off of thesupply of the fuel gas to the fuel-gas-spraying nozzles 413 a and 413 c.On the other hand, the line for supplying the oxygen-containing-gas tothe oxygen-containing-gas spraying nozzles 413 b and 413 d at themounting portion B includes switching valves 416 b and 416 d forcontrolling on/off of supply of the oxygen-containing-gas to the nozzles413 b and 413 d. Here, each of the switching valves 416 a, 416 b, 416 c,and 416 d, are controlled by the supply controller 420 b.

Thus, the supply controllers 420 a and 420 b control on/off of thenozzles, thereby selecting the nozzles to be used for spraying the fuelgas and the oxygen-containing-gas to the combustion chamber 410.

Thus, in the tubular flame burner according to the present embodiment,the number of the nozzles to be used for combustion is suitably selectedfrom the multiple combustion-gas spraying nozzles andoxygen-containing-gas spraying nozzles. Controlling on/off of theswitching valves does such a way, and this way is as well as adjustingthe flow supplied to each nozzle by controlling the correspondingregulator, so as to obtain a predetermined spraying speed. It ends up insuppressing the pressure loss when the supply flow increases, as well asmaintaining formation of a swirl when the supply flow reduces. Even inthe event of change in the total supply flow of the fuel gas and theoxygen-containing-gas corresponding to change in the combustion load,the above-mentioned procedure is done.

Note that the tubular flame burner according to the present embodimentmay also be formed with a polygonal cross-sectional shape rather thanround.

Embodiment 5-3

FIG. 23 through FIG. 25 show an embodiment 5-3 according to the presentinvention. FIG. 23 is a side view of a tubular flame burner according tothe present embodiment, FIG. 24A is a cross-sectional view taken alongline A-A in FIG. 23, and FIG. 24B is a cross-sectional view taken alongline B-B in FIG. 23. FIG. 25 is an overall configuration diagram, whichshows a combustion controller for the tubular flame burner according tothe present embodiment.

In FIG. 23, reference numeral 410 is a tubular combustion chamber,wherein the one end 410 a opens so as to serve as an exhaust vent forcombustion exhaust gas. Furthermore, the tubular combustion chamber 410includes two nozzle-mounting portions A and B along the tube axis on theside of the rear-end 410 b thereof for spraying a fuel gas and anoxygen-containing-gas to the combustion chamber 410.

At the nozzle-mounting portion A, two long and narrow slits 432extending along the tube axis are formed along the circumferential wallof the combustion chamber 410, so as to serve as nozzles for thecombustion chamber 410. And such slits are connected to nozzles 431 aand 431 b, formed flat, and long and narrow along the tube axis,respectively, as shown in FIG. 23 and FIG. 24A. These nozzles 431 a and431 b are disposed so that each spraying direction thereof is in atangential direction of the inner circumferential wall of the combustionchamber 410 so as to form a swirl in a predetermined direction. Notethat a premixed gas wherein the fuel gas and the oxygen-containing-gashave been mixed beforehand is supplied to the nozzles 431 a and thenozzles 431 b.

The premixed gas is sprayed in the tangential direction of thecircumferential wall of the combustion chamber 410 at a high speed fromthe premixed-gas spraying nozzles 431 a and 431 b to which the premixedgas is supplied. This is done so as to form a swirl at a region near theinner circumferential wall of the combustion chamber 410. When thepremixed gas forming such a swirl by an ignition device (not shown) suchas an ignition plug, pilot burner, or the like, are ignited, atube-shaped flame is formed within the combustion chamber 410.

In the same way, at the nozzle-mounting portion B, two long and narrowslits 434 extending along the tube axis are formed along thecircumferential wall of the combustion chamber 410, so as to serve asnozzles for the combustion chamber 410. And such slits are connected tonozzles 433 a and 433 b, formed flat, and long and narrow along the tubeaxis, respectively, as shown in FIG. 23 and FIG. 24B. These nozzles 433a and 433 b are disposed so that each spraying direction thereof is in atangential direction of the inner circumferential wall of the combustionchamber 410 so as to form a swirl in a predetermined direction. Notethat a premixed gas wherein the fuel gas and the oxygen-containing-gashave been mixed beforehand is supplied to the nozzles 433 a and thenozzles 433 b.

The premixed gas is sprayed in the tangential direction of thecircumferential wall of the combustion chamber 410 at a high speed fromthe premixed-gas spraying nozzles 433 a and 433 b to which the premixedgas is supplied. This is done, so as to form a swirl at a region nearthe inner circumferential wall of the combustion chamber 410. When thepremixed gas forming such a swirl by an ignition device (not shown) suchas an ignition plug, pilot burner, or the like are ignited, atube-shaped flame is formed within the combustion chamber 410.

As described above, the tubular flame burner according to the presentembodiment includes two nozzles that set along the tube axis. Each ofthese nozzles are formed of two premixed-gas spraying nozzles along asingle circumference of the combustion chamber, i.e., the tubular flameburner according to the present embodiment includes four premixed-gasspraying nozzles.

Furthermore, as shown in FIG. 25, the lines for supplying the premixedgas to the premixed-gas spraying nozzles 431 a, 431 b, 433 a, and 433 b,include switching valves 435 a, 435 b, 436 a, and 436 b, for controllingon/off of the supply of the premixed gas to the nozzles 431 a, 431 b,433 a, and 433 b, respectively. And the lines further include gas mixers437 a, 437 b, 438 a, and 438 b, for premixing the fuel gas and theoxygen-containing-gas beforehand, respectively.

The supply controller 420, thereby enabling the nozzles to beselectively used for spraying the premixed gas to the combustion chamber410, performs on/off control of the switching valves 435 a, 435 b, 436a, and 436 b.

The line for supplying the fuel gas to the gas mixers 437 a, 437 b, 438a, and 438 b, includes a fuel-gas-flow regulator 417 for adjusting thetotal flow of the fuel gas to be supplied. On the other hand, the linefor supplying the oxygen-containing-gas to the gas mixers 437 a, 437 b,438 a, and 438 b, includes an oxygen-containing-gas-flow regulator 418for adjusting the total flow of the oxygen-containing-gas to besupplied. The fuel-gas-flow regulator 417 and theoxygen-containing-gas-flow regulator 418 are controlled by the supplycontroller 420 so as to adjust the total flow of the fuel gas and thetotal flow of the oxygen-containing-gas, which are to be supplied,corresponding to the combustion load. That is to say, when a combustionload is small, the apertures of the fuel-gas-flow regulator 417 and theoxygen-containing-gas-flow regulator 418 reduces, so as to reduce thetotal supply flow. On the other hand, when a combustion load is great,the apertures of the fuel-gas-flow regulator 417 and theoxygen-containing-gas-flow regulator 418 increase so as to increase thetotal supply flow.

Note that the flow-meter 421 for the fuel gas and the flow-meter 422 forthe oxygen-containing-gas measure each of the total supply flow of thefuel gas and the oxygen-containing-gas. And the measurement results aresent to the supply controller 420, so as to be used for adjusting theapertures of the fuel-gas-flow regulator 417 and theoxygen-containing-gas-flow regulator 418.

Combustion control with the combustion controller for a tubular flameburner having such a configuration is performed in the same way as withthe above-described embodiment.

That is to say, the number of the nozzles to be used for spraying thepremixed gas is adjusted by the supply controller 420 controlling on/offof the switching valves 435 a, 435 b, 436 a, and 436 b, corresponding tothe combustion load, so that the initial flow speed of the premixed gassprayed to the combustion chamber is maintained in a range between themaximal permissive flow speed Vp dependent upon the pressure loss andthe minimal flow speed Vq required for forming a tube-shaped flame.

For example, when a combustion load is fallen within a range from thepredetermined minimal combustion load to a load of approximately ¼, asingle nozzle for spraying the premixed gas is used. And when acombustion load is fallen within a range from a load of approximately ¼to approximately ½ thereof, two nozzles for spraying the premixed gasare used. Furthermore, when a combustion load is fallen within a rangefrom a load of approximately ½ to the predetermined maximal combustionload, four nozzles for spraying the premixed gas are used.

Thus, the initial flow speed from the spraying nozzles is obtainedwithin a range between the maximal permissive flow speed Vp (dependentupon the pressure loss) and the minimal flow speed Vq (required forforming a tube-shaped flame), thereby suppressing excessive pressureloss while maintaining the high speed of the flow required for forming atube-shaped flame.

As described above, the tubular flame burner according to the presentembodiment includes two nozzles that set along the tube axis. Each ofthese nozzles is formed of two nozzles for spraying the premixed gas,along a single circumference of the tubular combustion chamber 410. Andthe tubular flame burner, wherein the number of the nozzles to be usedfor combustion, is suitably selected from the multiple nozzles forspraying the premixed gas, by controlling on/off of the switching valvesso as to exhibit a predetermined flow speed, even in a case of change inthe total supply flow of the premixed gas corresponding to change in thecombustion load, thereby suppressing the pressure loss at the time of anincrease of the supply flow, as well as maintaining formation of a swirlat the time of reduction of the supply flow.

Note that description has been made in the present embodiment regardingthe tubular flame burner including two nozzles that sets along the tubeaxis. Each of these nozzles is formed of two nozzles for spraying thepremixed gas along a single circumference thereof. The tubular flameburner may include a suitable number of nozzle sets along the tube axis,each of which are formed of a suitable number of nozzles for sprayingthe premixed gas along a single circumference thereof, as appropriate.

Furthermore, description has been made in the present embodimentregarding the arrangement, wherein the nozzles for spraying the premixedgas are disposed so that each spraying direction is in a tangentialdirection of the inner circumferential wall of the combustion chamber.An arrangement according to the present invention is not restricted tothe aforementioned arrangement. An arrangement may be made wherein anyspraying direction is not in a tangential direction of the innercircumferential wall of the combustion chamber as long as a swirl of amixture gas is formed within the combustion chamber.

Furthermore, while description has been made in the present embodimentregarding the arrangement, wherein the slits serving as the nozzles forthe combustion chamber are disposed along the tube axis, and each slitis connected to the corresponding flat nozzle for spraying the premixedgas. An arrangement may be made wherein multiple small-sized openingsare formed along the tube axis, and each nozzle is connected to thecorresponding array formed of the small-sized openings for spraying thepremixed gas.

Furthermore, in the present embodiment, a gas formed by preheatingliquid fuel may be employed as a fuel gas. Note that liquid fuel whichreadily evaporate under relatively low temperature, such as kerosene,gas oil, alcohol, A-type heave oil, or the like, is suitably employed asthe liquid fuel.

Note that the tubular flame burner according to the present embodimentmay also be formed with a polygonal cross-sectional shape rather thanround.

Embodiment 5-4

The present embodiment is shown in FIG. 27. FIG. 27 is an overallconfiguration diagram, which shows a combustion controller for a tubularflame burner according to the present embodiment.

The combustion controller according to the above-described embodiment5-3 has a configuration. Here, the total flow of the fuel gas and thetotal flow of the oxygen-containing-gas, which are to be supplied to thepremixed-gas spraying nozzles at the mounting portion A and/or to thefuel-gas spraying nozzles at the mounting portion B, are adjusted asshown in FIG. 25. The combustion controller according to the presentembodiment has a configuration wherein the fuel-gas flow and theoxygen-containing-gas flow, which are to be supplied to the premixed-gasspraying nozzles at the mounting portion A, are independently adjusted.

That is to say, as shown in FIG. 26, the line for supplying the fuel gasto the premixed spraying nozzles 431 a and 431 b at the mounting portionA includes the fuel-gas flow regulator 417 a for adjusting the flow ofthe fuel-gas, which is to be supplied. On the other hand, the line forsupplying the oxygen-containing-gas to the premixed spraying nozzles 431a and 431 b at the mounting portion A includes theoxygen-containing-gas-flow regulator 418 a for adjusting the flow of theoxygen-containing-gas, which is to be supplied. The fuel-gas-flowregulator 417 a and the oxygen-containing-gas-flow regulator 418 a arecontrolled by the supply controller 420 a, thereby enabling the fuel-gasflow and the oxygen-containing-gas flow to be adjusted, which are to besupplied to the premixed-gas spraying nozzles 431 a and 431 b at themounting portion A. The supply flow of the fuel gas and the supply flowof the oxygen-containing-gas are measured by the flow-meter 421 a forthe fuel gas and the flow-meter 422 a for the oxygen-containing-gas,respectively. And the measured results are sent to the supply controller420 a, so as to be used for adjusting the apertures of the fuel-gas-flowregulator 417 a and the oxygen-containing-gas-flow regulator 418 a.

In the same way, the line for supplying the fuel gas to the premixedspraying nozzles 433 a and 433 b at the mounting portion B includes thefuel-gas-flow regulator 417 b for adjusting the flow of the fuel gaswhich is to be supplied. On the other hand, the line for supplying theoxygen-containing-gas to the premixed spraying nozzles 433 a and 433 bat the mounting portion B includes the oxygen-containing-gas-flowregulator 418 b for adjusting the flow of the oxygen-containing-gas,which is to be supplied. The supply controller 420 b controls thefuel-gas-flow regulator 417 b and the oxygen-containing-gas-flowregulator 418 b. Such a controlling method makes it possible to adjustthe fuel-gas flow and the oxygen-containing-gas flow, which are to besupplied to the premixed-gas spraying nozzles 433 a and 433 b at themounting portion B, and the flow-meter for the oxygen-containing-gas.The supply flow of the fuel gas and the supply flow of theoxygen-containing-gas are measured by the flow-meter 421 b for the fuelgas and the flow-meter 422 b for the oxygen-containing-gas,respectively. And the measured results are sent to the supply controller420 b so as to be used for adjusting the apertures of the fuel-gas-flowregulator 417 b and the oxygen-containing-gas-flow regulator 418 b.

The supply controller 420 a for the premixed-gas spraying nozzles 431 aand 431 b at the mounting portion A, and the supply controller 420 b forthe premixed-gas spraying nozzles 433 a and 433 b at the mountingportion B, are interconnected each other for adjusting the total supplyflow of the fuel gas and the oxygen-containing-gas.

Note that the line for supplying the premixed gas to the premixed-gasspraying nozzle 431 a at the mounting portion A from the gas mixer 437 aincludes the switching valve 435 a for controlling on/off of supply ofthe premixed gas to the premixed-gas spraying nozzle 431 a. And the linefor supplying the premixed gas to the premixed-gas spraying nozzle 431 bat the mounting portion A from the gas mixer 437 b includes theswitching valve 435 b for controlling on/off of supply of the premixedgas to the premixed-gas spraying nozzle 431 b.

On the other hand, the line for supplying the premixed gas to thepremixed-gas spraying nozzle 433 a at the mounting portion B from thegas mixer 438 a includes the switching valve 436 a for controllingon/off of supply of the premixed gas to the premixed-gas spraying nozzle433 a. And the line for supplying the premixed gas to the premixed-gasspraying nozzle 433 b at the mounting portion B from the gas mixer 438 bincludes the switching valve 436 b for controlling on/off of supply ofthe premixed gas to the premixed-gas spraying nozzle 433 b.

On/off control of the switching valves 435 a and 435 b is performed bythe supply controller 420 a. And on/off control of the switching valves436 a and 436 b is performed by the supply controller 420 b. The nozzlesto be used for spraying the premixed gas to the combustion chamber 410are selected by the aforementioned on/off control.

Thus, in the present embodiment, the number of the nozzles to be usedfor combustion is suitably selected from the multiple nozzles forspraying the premixed gas, by controlling on/off of the switchingvalves. And the flow supplied to each nozzle is adjusted by controllingthe corresponding flow regulator, so as to exhibit a predetermined flowspeed. This is done, even in a case of change in the total supply flowof the premixed gas corresponding to change in the combustion load. Thismakes it possible to suppress the pressure loss when an increase of thesupply flow increases, as well as maintaining formation of a swirl atthe time of reduction of the supply flow.

In the present embodiment, the number of the nozzles to be used forspraying the fuel gas and the oxygen-containing-gas to the combustionchamber, or the number of the nozzles to be used for spraying thepremixed gas formed of the fuel gas and the oxygen-containing-gas to thecombustion chamber, is suitably selected so as to exhibit apredetermined spraying speed. This is done, even in case of change inthe total supply flow of the fuel and oxygen-containing-gascorresponding to change in the combustion load, thereby achieving stablecombustion in a wider range of the combustion load.

Note that the tubular flame burner according to the present embodimentmay also be formed with a polygonal cross-sectional shape rather thanround.

Embodiment 6

FIG. 28 through FIG. 31 show an embodiment 6 according to the presentinvention. FIG. 28 is a side view of a tubular flame burner according tothe present embodiment, FIG. 29A is a cross-sectional view taken alongline A-A in FIG. 28. FIG. 30 is an overall configuration diagram whichshows a combustion controller for the tubular flame burner according tothe present embodiment, and FIG. 31 is an explanatory diagram fordescribing a combustion control method for the tubular flame burneraccording to the present embodiment.

In FIG. 28, reference numeral 510 denotes a tubular combustion chamber,wherein the front-end 510 a opens so as to serve as an exhaust vent fora combustion exhaust gas. Furthermore, the combustion chamber 510includes nozzles for spraying a fuel gas to the combustion chamber 510,and nozzles for spraying an oxygen-containing-gas thereto, near therear-end 510 thereof.

As shown in FIG. 28 and FIG. 29, the combustion chamber 510 includesfour long and narrow slits 512 arrayed along a single tubecircumference. Each of these slits are formed long along the tube axisthereof, so as to serve as nozzles for the combustion camber 510, whichare connected to nozzles 511 a, 511 b, 511 c, and 511 d, formed flat,long and narrow along the tube axis thereof, respectively. These nozzles511 a, 511 b, 511 c, and 511 d, are disposed so that each sprayingdirection is in a tangential direction of the inner circumferential wallof the combustion chamber 510 so as to form a swirl in a predetermineddirection. Of these four nozzles, the nozzles 511 a and 511 c serve asfuel-gas spraying nozzles, and the nozzles 511 b and 511 d serve asoxygen-containing-gas spraying nozzles.

The fuel gas is sprayed in the tangential direction of the innercircumferential wall of the combustion chamber 510 at a high speed fromthe fuel-gas spraying nozzles 511 a and 511 c. And, theoxygen-containing-gas is sprayed in the tangential direction of theinner circumferential wall of the combustion chamber 510 at a high speedfrom the oxygen-containing-gas spraying nozzles 511 b and 511 d, so asto form a swirl while efficiently mixing the fuel gas and theoxygen-containing-gas at a neighborhood region of the innercircumferential wall of the combustion chamber 510. When the mixture gasforming a swirl the tubular flame burner is ignited by an ignitiondevice (not shown) such as an ignition plug, pilot burner, or the like,a tube-shaped flame is formed within the combustion chamber 510. Acombustion gas therefrom is discharged from the front-end 510 a of thecombustion chamber 510.

Note that the oxygen-containing-gas represents a gas for carrying oxygenused for combustion such as air, oxygen, oxygen-enriched air, exhaustmixture gas, or the like.

Furthermore, as shown in FIG. 29A and FIG. 29B, a slit apertureadjusting ring 513 is disposed at a portion, where the slits 512 aredisposed, so as to be in contact with the inner wall of the combustionchamber 510 for adjusting the apertures of the slits 512. The slitaperture-adjusting ring 513 is formed in the shape of a tube with asmall thickness. The slit aperture includes four slots along thecircumferential direction corresponding to the four slits 512, whereinthe apertures of the four slits 512 are adjusted by rotating the slitaperture adjusting ring 513 in the direction of the tube circumference.

Specifically, FIG. 29A shows the combustion chamber 510, wherein theslots of the slit aperture adjusting ring 513 just matches with thecorresponding slits 512, so as to adjust the aperture of each slit 512to the maximum. FIG. 29B shows the combustion chamber 510, wherein theslit aperture adjusting ring 513 is rotated by a certain angle from thestate shown in FIG. 29A, so that a part of each slit 512 is closed withthe slit aperture adjusting ring 513 so as to reduce the aperture ofeach slit 512.

Furthermore, as shown in the overall configuration diagram in FIG. 30,with the combustion controller for the tubular flame burner according tothe present embodiment, the line for supplying the fuel gas includes thefuel-gas-flow regulator 517 for adjusting the flow of the fuel gas to besupplied to the fuel-gas spraying nozzles 511 a and 511 c, and the linefor supplying the oxygen-containing-gas includes theoxygen-containing-gas-flow regulator 518 for adjusting the flow of theoxygen-containing-gas to be supplied to the oxygen-containing-gasspraying nozzles 511 b and 511 d. The supply controller 520, so as toadjust the supply flow of the fuel gas and the oxygen-containing-gascorresponding to the combustion load, controls the fuel-gas-flowregulator 517 and the oxygen-containing-gas-flow regulator 518.Specifically, in case of a small combustion load, the apertures of thefuel-gas-flow regulator 517 and the oxygen-containing-gas-flow regulator518 are reduced, so as to reduce the supply flow thereof. On the otherhand, in case of a great combustion load, the apertures of thefuel-gas-flow regulator 517 and the oxygen-containing-gas-flow regulator518 are increased so as to increase the supply flow thereof.

Note that the supply flow of the fuel gas and the supply flow of theoxygen-containing-gas are measured by the flow-meter 521 for the fuelgas and the flow-meter 522 for the oxygen-containing-gas, respectively.And the measurement results are sent to the supply controller 520 so asto be used for adjusting the apertures of the fuel-gas-flow regulator517 and the oxygen-containing-gas-flow regulator 518.

Furthermore, a motor 514 is provided for adjusting the angular positionof the slit aperture adjusting ring 513, is controlled by the supplycontroller 520, and adjusts the apertures of the slits 512 bycontrolling the angular position of the slit aperture adjusting ring513. Note that an actuator such as a hydraulic cylinder, an aircylinder, or the like, may be employed instead of the motor 514.

Description will be made regarding a combustion control method for thetubular flame burner having such a configuration with reference to FIG.30 and FIG. 31.

In the method for controlling the combustion by the tubular flameburner, when the supply flow is variable and changes corresponding tothe combustion load, the apertures of the slits 512 are adjusted in thefollowing way. That is, the initial flow speed of the fuel gas and theoxygen-containing-gas sprayed to the combustion chamber 510 ismaintained within a range from the maximal permissive flow speed Vp(dependent upon the pressure loss) and the minimal flow speed Vq(required for forming a tube-shaped flame).

Specifically, as shown by the line L₁ in FIG. 31A, when the apertures ofthe slits 512 reduces, the initial flow speed of the flow from thespraying nozzles 511 a through 511 d exhibits a rapid increasecorresponding to the increased supply flow, i.e., the increasedcombustion load. As a result, while the flow speed rapidly reaches theminimal flow speed Vq (required for forming a tube-shaped flame), theflow speed rapidly exceeds the maximal permissive flow speed Vp(dependent upon the pressure loss).

On the other hand, when the apertures of the slits 512 somewhatincreases, the initial flow speed of the flow from the spraying nozzlesexhibits a relatively gentle increase thereof corresponding to theincreased supply flow, i.e., the increased combustion load, as shown bythe line L₂ in FIG. 31A. As a result, while the flow speed relativelyslowly reaches the minimal flow speed Vq (required for forming atube-shaped flame), the flow speed relatively slowly exceeds the maximalpermissive flow speed Vp (dependent upon the pressure loss).

Furthermore, when the apertures of the slits 512 increases to themaximum, the initial flow speed of the flow from the spraying nozzlesexhibits an extremely gentle increase thereof corresponding to theincreased supply flow, i.e., the increased combustion load, as shown bythe line L₃ in FIG. 31A. As a result, while the flow speed considerablyslowly reaches the minimal flow speed Vq (required for forming atube-shaped flame), the flow speed considerably slowly exceeds themaximal permissive flow speed Vp (dependent upon the pressure loss).

In the present combustion control method, the supply controller 520controls the angular position of the slit aperture adjusting ring 513,so as to adjust the apertures of the slits 512 such that the initialflow speed of the fuel gas. And the oxygen-containing-gas sprayed to thecombustion chamber 510 is maintained in a range between the maximalpermissive flow speed Vp (dependent upon the pressure loss) and theminimal flow speed (Vq required for forming a tube-shaped flame basedupon the above-described relation).

Specifically, as shown in FIG. 31B, in case of a combustion load in arange between the predetermined minimal combustion load to approximately⅓ of the predetermined maximal combustion load, the apertures of theslits 512 are reduced. In case of combustion load in a range betweenapproximately ⅓ of the predetermined maximal combustion load toapproximately ⅔ thereof, the apertures of the slits 512 somewhatincreases. Furthermore, in case of a combustion load in a range betweenapproximately ⅔ of the predetermined maximal combustion load to thepredetermined maximal combustion load, the apertures of the slits 512increases to the maximum, to perform combustion.

Thus, as shown by the line M1 in FIG. 31A, the initial flow speed fromthe spraying nozzles is maintained within a range from the maximalpermissive flow speed Vp (dependent upon the pressure loss) and theminimal flow speed (Vq required for forming a tube-shaped flame),resulting in suppressing excessive pressure loss while maintaining thehigh speed of the flow required for forming a tube-shaped flame.

Description has been made regarding the method for controlling thecombustion, wherein the apertures of the slits 512 are adjusted in astep-wise way, corresponding to the combustion load. But it may be acase, a combustion control is performed, wherein the apertures of theslits 512 are continuously adjusted corresponding to the combustion loadas shown in FIG. 318. In such a way, the initial flow speed from thespraying nozzles is maintained within a range from the maximalpermissive flow speed Vp (dependent upon the pressure loss) to theminimal flow speed Vq (required for forming a tube-shaped flame) whilemaintaining a constant flow speed, as shown by the line M2 in FIG. 31A.

Note that while description has been made in the present embodimentregarding the arrangement, wherein the fuel-gas spraying nozzles and theoxygen-containing-gas spraying nozzles are disposed so that eachspraying direction is in a tangential direction of the innercircumferential wall of the combustion chamber. The arrangement of thepresent invention is not restricted to the aforementioned arrangement.Another arrangement may be made, wherein any spraying direction is notin a tangential direction of the inner circumferential wall of thecombustion chamber as long as a swirl of the gas is formed within thecombustion chamber.

Furthermore, description has been made in the present embodimentregarding the arrangement, wherein the slits serving as the nozzles forthe combustion chamber are disposed along the tube axis, may be a case,that each slit is connected to the corresponding fuel-gas sprayingnozzle or oxygen-containing-gas spraying nozzle. In such a case, thenozzle has been formed flat, an arrangement may be made wherein multiplesmall-sized openings are formed along the tube axis, and each of thefuel-gas spraying nozzles and the oxygen-containing-gas spraying nozzlesare connected to the corresponding array formed of the small-sizedopenings.

Furthermore, description has been made in the present embodimentregarding the arrangement wherein the fuel gas is sprayed, anotherarrangement may be made wherein liquid fuel is sprayed. Note that liquidfuel which readily evaporate under relatively low temperature, such askerosene, gas oil, alcohol, A-type heave oil, or the like, is suitablyemployed as the liquid fuel.

Furthermore, description has been made in the present embodimentregarding the arrangement wherein the fuel gas and theoxygen-containing-gas are separately sprayed, an arrangement may be madewherein a mixture gas formed by premixing the fuel gas and theoxygen-containing-gas is sprayed.

According to the present embodiment, the apertures of the nozzleorifices are adjusted so as to exhibit a predetermined flow speed. Thisis done, even in case of change in the supply flow of the fuel and theoxygen-containing-gas corresponding to change in the combustion load,thereby enabling stable combustion to be in a wider range of thecombustion load.

Note that the tubular flame burner according to the present embodimentmay also be formed with a polygonal cross-sectional shape rather thanround one.

1. A tubular flame burner comprising: a tubular combustion chamberhaving two ends, wherein one end is an open front-end and the other endis a rear-end to which an ignition device is mounted; and fuel-gasspraying nozzles and oxygen-containing-gas spraying nozzles, whereinrespective orifices of the respective nozzles face toward an innersurface of the combustion chamber, so as to spray a fuel-gas and anoxygen-containing-gas in the neighborhood of a tangential direction ofan inner circumferential wall of the combustion chamber; wherein anignition device is disposed at a position between a point of a tube axisextending along a longitudinal direction of the combustion chamber, anda point of an axis apart away, by ½ of a radius of the combustionchamber, from the point of the tube axis along a cross-sectionaldirection orthogonal to the longitudinal direction.
 2. The tubular flameburner according to claim 1, further comprising means for decreasing aflow speed of a swirl of a mixture gas of the fuel and theoxygen-containing-gas, while mixing the fuel with theoxygen-containing-gas, in order for air excess ratio to fall within apredetermined scope.
 3. The tubular flame burner according to claim 1,wherein the respective nozzles include respective nozzle-orifices forspraying the gas and include a plurality of small-sized opening arrays,disposed along the tube axis, to serve as the nozzle orifices forspraying the gas; and wherein the respective nozzles are connected tothe small-sized opening arrays.